Lainie B

No. She can marry you, apply for AOS(I-485 and I-130 concurrently) and legally stay. She will be in a new period of authorized stay when she files to adjust status. At the same time, she can apply for I-765(EAD-work authorization) and I-131(AP-advance parole for travel). The fees for those are waived when filed with a pending I-485. They take about 60-90 days to receive. She would not be able to leave the US until she had the AP or green card though, or she would abandon the AOS process. So, she would need to decide if she could wait a few more months to visit her family, or if she would rather go back home, and then wait for the K-1 process before coming back to marry you.
Once she gets the green card, she can travel easily to visit her family when she wishes. Sometimes AOS only takes a few months to complete. It would depend on how busy your local USCIS office is as to how soon you would have the interview.

Can you post the answer here? I bet future Australian K-1 applicants will be equally confused

Yes you can file now for free with a copy of your I-485 NOA1. It may not take too long since you have your EAD already. It won't affect your I-485.

What on earth has you military background got to do with anything?

Your petition got approved, not the visa. Your fiance hasn't even applied for the visa yet. With an approved petition, he is eligible to apply for the K-1 visa.

If she didn't fully understand the prenup when she signed it, and it sounds like she didn't, then it won't count in a divorce. You should have hired her a lawyer to explain it to her at the time of signing.

If she didn't fully understand the prenup when she signed it, and it sounds like she didn't, then it won't count in a divorce. You should have hired her a lawyer to explain it to her at the time of signing.

If she didn't fully understand the prenup when she signed it, and it sounds like she didn't, then it won't count in a divorce. You should have hired her a lawyer to explain it to her at the time of signing.

He won't need a work permit, as he will have a green card upon entry into the US. He will be able to work right away. At no stage does he need the I-485 or I-765.

He won't need a work permit, as he will have a green card upon entry into the US. He will be able to work right away. At no stage does he need the I-485 or I-765.

No, you are misunderstanding the requirement. They must have met in person within the last two years. They don't need to have been in a relationship for over two years.

No, you are misunderstanding the requirement. They must have met in person within the last two years. They don't need to have been in a relationship for over two years.

No, you are misunderstanding the requirement. They must have met in person within the last two years. They don't need to have been in a relationship for over two years.

Did you try asking her what she'd like to do? Or what interests her?
I sure like weighing in on what I might do with my time, as opposed to having someone tell me.
I'm guessing she probably has some thoughts about it.

If you are in the US right now, you could get married & file for AOS...

Your SSN was not temporary and it hasn't expired. It's your number for life and you should write it on the form. When you get to the US you'll be able to use the same number again. When you get your EAD or green card, you'll use that number for work.
If you've had an A-number in the past then yes you should write it on the form.
I doubt you'll get any useful information by calling USCIS, they are more likely to give you the wrong information.

You are misunderstanding. She is not eligible for US citizenship after three years of being in the US, she is eligible after 3 years of being a legal permanent resident. She needs to take a look at her green card and see what is the "resident since" date. That is the date she needs to use to calculate her eligibility.
And yes, she needs to apply for ROC first by submitting form I-751. The ROC application is the application for her 10-year green card. It is not two separate applications.

Not just being married to a US citizen for three years. She must be a legal permanent resident for 3 years.

Not just being married to a US citizen for three years. She must be a legal permanent resident for 3 years.

You are sending far too much evidence. Think about it, someone is going to have to scan, file and then read through every page you submit. You need to cut way back on the evidence you send. My I-751 form and evidence all fit into a normal sized priority envelope and was approved without an RFE.

Think about it. Would USCIS have a single, "residential-sized" literal box for ALLLLL of the applications they will receive? Do you really believe that packages are sent to a small box one at a time with any single package filling up all the space?

For the I-751, the "petitioner" is the applicant, ie the green card holder. So where the form asks for "petitioner's signature", that is you. "Spouse's signature" is for the US citizen

For the I-751, the "petitioner" is the applicant, ie the green card holder. So where the form asks for "petitioner's signature", that is you. "Spouse's signature" is for the US citizen

You should get your name removed from the Australian electoral roll otherwise you will get fined for not voting.
Keeping a bank account open is no big deal and can come in handy when visiting. If the account is interest-bearing it is important to change the address to your new overseas one so that the bank will correctly charge withholding tax, this will save you headaches during tax return time.

The EAD is free when you apply with adjustment of status. Where are you getting that it costs $400? If you had submitted form I-765 (for free) when you submitted the I-485, you would have got the EAD within 60-90 days of applying.
Your green card is taking unusally long, have you inquired with USCIS?
You were not working "potentially" without authorization, you were working illegally.