I'm sorry for what all you've been through, what with health issues and envy and your h's NRE.
I agree, you need to learn to say "no," and know what your needs are and make your wishes known. This summer I was under a lot of stress, and Ginger was trying to date 3 people and it drove me batty, dealing with hearing about them and all the various issues around them getting together.
My stressors were: a move to a new house (moving in with my gf and getting used to that, plus unpacking, getting to know the new town), my gf having big traumas at work and in her family, which triggered her anxiety issues, and then me having a date with a guy who then tried to commit suicide. Having Ginger dating through all that sent me over the edge!
And you had cancer and surgery! I'd have to say that is even more stressful.
As far as your bad date with Puking Guy, how could that have gone better? For me, no hard drinking, and no sex on a first date seems to help. You can only do so much weeding of OKC guys in chat and on the phone before that first date. I always meet in public, I don't have more than 2 drinks, and I don't take them home, even for making out. Some/most guys will say and do anything to get laid. So, they may seem like Mr Right, until that first shag. Then their true colors come out. If they are right for you, they will be willing to have a date or two in public before they want sex.
I've learned all this from doing things wrong!