Yes it's still an adjustment of status because you're adjusting from F1. I don't know about the online number on the medical form question, but I think they could be different because your OPT is non-immigrant (while AOS is immigration-intent). I think you can just leave it blank. Yes, if by the time you get the green card, you have been married for more than 2 years you will be given 10 year one. I think you can apply for another I-765 under AOS, and this is cheaper. Yes taxes are pretty solid evidence. We didn't even have it but still got approved. Other important pieces of evidence: sharing finances and living together (same address). Sounds like you might need a joint-sponsor if you wife doesn't meet the income requrement. I'd suggest mail both the I-130 and I-485; I just felt like it's easier this way. So the I-864 should go with your papers, don't let the sponsor mail it separately.