JimVaPhuong

According to the INA section 212(h), the only controlled substance violation that is waiver eligible is a single offense involving simple possession of marijuana, less than 30 grams. I don't see any provision that would allow someone convicted of possession of any other controlled substance, including cocaine, to be eligible for a waiver.
I'm sorry, but I don't think there is any way your fiance can get a visa. If you decide to consult with a lawyer I strongly suggest you thoroughly educate yourself about the relevant immigration law before you hire anyone, especially section 212 of the INA. There are, unfortunately, lawyers who prey on people in your position.

Even better! Show that you had planned to return within 6 months, but that circumstances arose that required you to be gone longer. Does the employment certificate explain that your employer asked you to finish out the school year AFTER you arrived? If not, would they be willing to write you a letter that explains this? This would sufficiently cover the reason for not getting a reentry permit.
Also, be sure you have something that shows you continued to maintain a residence in the US while you were gone.

Obviously, you already know the basic facts about this. The CBP is allowed to presume that he abandoned his residency if he's gone more than 6 months. The four points they consider are:
1. Intent on departure from the US
2. Whether travel has a specific purpose, and a specific ending date
3. Whether the LPR paid taxes while abroad
4. Ties to the US (residence, bank accounts, etc.)
In your case, 1 and 2 may be related. If he knew his absence was going to be temporary, and for a specific purpose and length of time, then he would have known he was going to be gone for more than 6 months and should have obtained a reentry permit. It sounds like you've got item 3 covered. Item 4 sounds like it's partially covered. Returning to stay with your parents is not the same thing as maintaining a residence, even if you were living with your parents before you left. CBP could conclude you abandoned your residence when you left, and are reestablishing it on your return. If you had evidence you were paying rent, and continued to pay rent while you were gone, your case would be a lot tighter.
Unfortunately, nobody can guarantee what the CBP is going to do in a case like this. Try to come up with as much evidence as you can that you knew the departure would be temporary when you left, and that your actions before and during the absence were consistent with the presumption that you would be returning. Have a good excuse ready for not having obtained a reentry permit before leaving.
Good luck!

Divorce will not affect his status, other than when he will be eligible for citizenship, as you mentioned.
There a many MANY websites that contain forms and advice on filing without an attorney. Do a Google search for "Illinois divorce forms" or "Illinois divorce law".
A "no fault" divorce in Illinois usually requires a 2 year period of separation. You can ask the judge to reduce the period to 6 months, but I think that's the best you're going to be able to do. If you need to file sooner than that, then you'll need to file based on fault. Adultery, while still technically a misdemeanor in Illinois, is very rarely prosecuted. Prosecutors consider it time consuming, costly, and largely pointless. Fornication is also, technically, a crime in Illinois. If they sought to prosecute for it then Oprah Winfrey would be facing a year in jail. There hasn't been a conviction for adultery in Illinois (that I was able to find) since 1943. A case was brought in Harvey, Illinois, in 1997, but the prosecutor refused to prosecute.
On the other hand, people divorce on the basis of adultery quite often in Illinois. There is no recent case (again, that I could find) where the divorce resulted in criminal prosecution of the accused adulterer.
Yes. No waiver needed if this will be your second K1, and it's been more than 2 years since your first K1 was approved.
Not likely to make any difference with the petition approval. Possible it might come up at the interview, but much less likely at the Embassy in London than with a high fraud consulate. Also possible it could come up at AOS or ROC, but not likely to be a problem.

Wait, I'm confused...
Didn't the Dems spend the last year telling us how bad the evil health insurance companies were? Didn't they change the name of this plan from "Healthcare Reform" to "Health Insurance Reform"? Now they're telling me that in 4 years I'm going to be required by law to to buy insurance from these evil companies?
Something else that's confusing me...
Didn't I hear someone say that the fine for not buying insurance is going to be around $700 per year? That works out to about $60 a month. Can anybody really get health insurance for only $60 a month, even with a government subsidy? Didn't I also hear someone say that the insurance companies won't be able to deny me coverage, even if I've got a pre-existing condition? Wouldn't it be cheaper just to pay the fine until I get sick, and then pay for the insurance until I'm well again?
Wait, I think I'm beginning to understand...
If the only people actually PAYING for health insurance are sick, then the insurance companies are going to be paying out a lot more than they're taking in. We'll punish those evil insurance companies by putting them out of business!
But wait... who will provide our health insurance after that? What sort of business can afford to operate in the red indefinitely without going out of business?

Minor point, but VAWA can only be used to adjust status if you're married to a US citizen who abused you. An abused fiancee has no basis to file a VAWA claim.
I also agree with others that this is not a material misrepresentation unless USCIS can somehow prove that she intentionally lied to the US government, either with the visa application, or upon entering the US. Unless they could prove that this course of action was planned in advance, I don't see how there's any misrepresentation.
Also, while she didn't satisfy the requirements of the K1 to qualify to apply for AOS, she didn't really "violate" anything. Aside from the overstay, everything she did appears to have been legal. You are correct in stating she blew her chance to get a green card, though.
I would also venture to guess that this is going to be a BIG mess at her next visa interview. She stayed in the US less than 9 months. In that period of time she managed to break up with the petitioner, move to Illinois, marry and subsequently break up with somebody else, and STILL managed to live for 6 months with her new boyfriend. If the consulate in Manila doesn't roast her over the coals at her next interview, I'll be absolutely amazed.

An I-601 is an application for a waiver of inadmissibility. That "inadmissibility" doesn't go away just because you're married. If he's inadmissible now, he'll still be inadmissible after you're married, and you'll still need the waiver.
The I-601 requires that you (the petitioner) prove extreme hardship. It is possible that you may have a better chance of proving extreme hardship for being separated from your husband than you would for being separated from your fiance, but your evidence needs to be very strong in either case. With all due respect to your mother's government friend, most people in the government actually know very little about the law unless they are involved in interpreting and applying that law on a daily basis. If your mother's friend is an immigration judge or consular officer (for example), then they may be able to help you. Otherwise, you need the advise and assistance of good immigration attorney who is experienced with I-601 waivers.
Even if he'd stayed in the US and you had married him, he would not have been able to get a green card because of his illegal entry. USCIS will waive an overstay for the spouse of a US citizen, but only if they entered the US legally. I don't know if there was any other route to legal status available to him while he was in the US, but I rather doubt it. Leaving the US may have been the only way to get started on a path to legal migration. I don't think you made a mistake.
He probably has a 10 year ban. You probably should have consulted with a good immigration lawyer from the start. You would have had your I-601 application ready to submit immediately after the interview. In any case, you should consult with an attorney now.

Yes, what you are required to submit does differ somewhat between the different consulates. They have wide latitude in determining the "public charge" requirements for a K1. Nearly all consulates will want, at minimum, a copy of the most recent year's tax return or transcript. Most consulates prefer transcripts because they are confirmation from the IRS that a return was filed, and what numbers were recorded on that return. Some consulates want 3 years of tax returns or transcripts.
At most consulates, if you have proof that current income meets the requirements, then it won't matter if the tax return doesn't show sufficient income. Generally, it's the consulates in high fraud countries that tend to more strict about the financial evidence.

It sounds like the only thing they're holding against him is the fact that he misrepresented himself, and not the fact that he worked illegally in the US. The INA doesn't specifically state how long a person is banned for misrepresentation. It only says that such a person is inadmissible. Section 235, which they mentioned, only describes that the CBP officer has the discretion to deny them entry or have them removed from the US. It's pretty much up to the discretion of DHS how long he is banned.
You can petition for a visa. Your petition will probably be approved, but his visa will be denied at the interview. You can submit an application for a waiver of the ban, but you must prove extreme hardship. These waivers can be tough to get. A good immigration lawyer with extensive experience with these sort of waivers is highly recommended.

I don't know how much time you think you'll need, but you may be able to buy enough time without having to cancel anything. The consulate will usually extend the validity of the approved petition, often for as long as a year. If that sounds like it might be enough time, then email the consulate and ask them about it. Often, the only thing that's required is that you inform them that you do intend to submit a visa application at some point. They may require you to reaffirm your intentions periodically. Once you submit the visa application, you usually have a month or two before the interview. Once the visa is issued, you have a further 6 months to actually use the visa to travel to the US.
So, in all, you might be able to postpone your arrival in the US for up to 20 months, depending on the consulate.
If you don't submit a visa application to the consulate then the petition will eventually expire on it's own. If you notify the consulate that you don't intend to submit a visa application, then the petition will expire 4 months after it was approved. Notifying them should prevent them from automatically extending the approval of the petition. Your fiance could also cancel the petition by notifying USCIS and the consulate (I think a notarized letter is required). However, this shouldn't be necessary.
A canceled or expired K1 petition should normally not affect your future ability to visit the US.

That's not really the point. Immigration is a multi-stage process. If there's a problem with your documents at any stage in the process, it would seem sensible to fix the problem while you're still in that stage, rather than try to retroactively fix it when you get to the next stage or some other stage further down the road. It also makes sense to fix the problem with the government agency where the problem originally occurred. I doubt USCIS will be very happy about being asked to adjudicate a green card application, while being simultaneously told that the visa upon which that green card application is based was approved by the consulate with incomplete information, and further being asked to correct that error. I could easily imagine USCIS saying that this should have been considered with original visa application, revoking the applicant's visa status, and sending them back to the consulate to reapply for the visa. Even though the missing information would clearly not have affected his eligibility to receive the visa, USCIS could simply say that it wasn't their call to decide that.
I don't see why they'd want another interview. The CO who approved your visa would only need to review your new documents and evidence. If he doesn't see any reason why it should change your visa approval (and it shouldn't) then he could simply add the new stuff to your case file and be done with it. People do the reverse all the time - their visa application is in administrative review, or it's been denied and is waiting for final review by the visa section chief, and they submit new evidence to the consulate. The new evidence doesn't always change the outcome, but at least it's added to the casefile, which is your main objective here. There's also no reason why they'd have to verify your identity via email. All you're asking for is advice on what to do. Since they would presumably give the same advice to anyone in the same situation, your identity should be irrelevant.
The timing is a problem, though. This doesn't sound like something that could be resolved within 7 days. It could take that long (or longer) just to get a response to your email.