HandsomeElectric

According to London's info on Wikipedia, it is
London (city), Greater London (County), and England (Country)
http://en.m.wikipedia.org/wiki/London

We're in the midst of this now ourselves with an accountant. The options listed above are your choices. However, you have to keep in mind that the choice between MFS and MFJ can be complicated; there are differences in how the foreign income is taxed based on type, state (of petitioner), and duration of marriage (they pro-rate on how much of the year you were married). There are also differences in exemptions between federal taxes and state taxes. So filing jointly, which is much more complicated, may not actually give you a significant tax benifit.

Actually a Canadian CAN stay up to 180 days per 365. However it is up to CBP officers to allow you to do so. If it looks to them like you're trying to immigrate (even if you're not) they will deny you. Without a job to go back to, schooling to do, or very strong ties to Canada, it's very likely you could be denied entry. In the USA you need to have a work visa to work remotely (unlike in Canada) so don't try that route either.
As Canadians we aren't entitled to anything or have any rights to enter the USA, even being married to a USC. We have the privledge of being able to visit as long as we can without a visa, but it's a fickle thing and dependant on an individual's decision.
I'm sorry we can't offer more support for your plans. We all want this to go as smoothly for you as possible. I was living with my husband in just under 8 months and had my green card within 9 months (exactly) of filing. Others have a shorter time and others have a longer time. It depends on the initial petition time frame, and how correct you are in your paperwork for the NVC. The good part is if your wife has a decent job and makes over the poverty guidelines, you shouldn't have any trouble with the Affidavit of Support.
Personally I suggest keeping your job and home in Canada and visiting your wife as frequently as you can. In between visits you can skype. My husband and I pretty much lived on Skype since we were only able to visit every 3 months.

I don't know if this is the case or not with the OP, but a lot of people don't know complicated details of immigration law until they spent some time reading the forms, the guides, checking on the forum, etc. So my opinion is that if someone asks a question that clearly shows they have not been spending enough time finding out about this, it's better to gently point out the problems and direct them to the guides -like Harpa, mimolicious and others did-, and not start accusing them of trying to "game the system". The fact that other people try to do so is not the fault of the OP. I feel the OP did not know that staying 5 months and 29 days is not going to be OK.
I'd be very, very impressed if you tell me that when you learned that you can't just wait in the US for the immigration approval, or other complicated details about whatever process you went through, you thought that all of them were obvious or knew them beforehand.

1. If you visit the US for 6 months at a time, you'd then have to prove you still have a full time job, a house, a lease, SOMETHING that would make you want to go back to Canada after that 6 months. If you do not have this, you will not be allowed to enter or they will give you an I-94 with a set expiration date lesser the 6 months.
2. You need to stay in Canada while doing the I-130 spousal visa. Your wife will have to prove domicile...house, job, etc.
3. IF you decide to come to the US for 6 months and then AOS you are committing visa fraud. This forum is a forum for people who apply for immigration the legal way so when you talk about possibly committing visa fraud, it gets a LOT of people on here REALLY angry because we've all paid thousands of dollars to get our loved ones into the US and that is like peeing down our necks and throwing us to the birds because we did it the legal way. (Just saying)
4. You are looking at a processing time of around 8-10 months. Worst case.
5. This is my personal opinion but it seems as if you are around the immigration stuff for a few years in Canada. Doesn't surprise me it took them over 3 years with no answer. I'm sure this will get removed but it is so frustrating when people continually want to game the system when everyone on this forum providing the help and knowledge are spending THOUSANDS of dollars to do this the RIGHT way to make sure there is NO way their loved ones will get deported etc.
*End Rant*
Stay in Canada. Keep your job. Keep your house/apartment. Visit on weekends. PROVE strong ties to Canada...via a job (letter from employer) house deed, mortgage, lease whatever you have for when you do come visit. Do not try to stay for 6 months at a time. Wait your turn like the rest of us. Don't risk being deported and permanently separated from your wife. That's so not fair to her. Not worth the risk.

I had this same questions a few months ago when I sent my I-130 (feb 2013).. I also live in Spain and had plans to move to mexico in July, so I thought I would be somewhere in the NVC process by the time I had to move, and I was wondering what to do. I did not get any answers to my question back then.
This is what ended up happening: I got my NOA2 within 38 days of my NOA1.. moved on to NVC, requested an expedite at the end of the NVC process (medical reasons), and now I already have my visa. My point is.. if you and your wife live together in Spain, then there's a high probability that you will have your NOA2 fairly quickly (2 months or less from your NOA1 date), which means you would start the NVC process in July.. and maybe end up with an interview in November. Of course, this is sort of a best case scenario.. but I think you should wait until your have your NOA2, and then you'll know what to do, depending on how much time has passed. If your NOA 2 comes after July then I think you'd be cutting it very close. If if comes after august then I would definitely write down the next county you're moving to as the interview consulate.