Some random thoughts....
1) My sitch is somewhat different from most folks', but the worst part of the A for me was the lies. We were supposed to be partners, and partners don't lie about things that relate to the partnership IMO. Everything about the A was awful. But the lies were the worst for me. The lies hurt far more than anything else.
2) I believe we have free choices WRT how we view the A. We all have our deal breakers, but we don't have the same ones.
I didn't (and don't) give much of a shit about the past - my choice to R was based on how I saw my future, and I still think that is the best approach to getting out of infidelity. In fact, that's how I got us together. I thought she'd never go out with me (which was really being unaware of reality ), but I saw my future as pining away for her even though I knew I'd probably connect with some other women. Expecting to be shot down, I asked her out. That way, I'd at least know if I had a chance or not. I feared rejection for monthse, but rejection was way, way better than not knowing. The same thinking led me to ask if she was cheating a few times, but she lied.
3) Affairs happen in good Ms, according to Shirley Glass, especially when the WS has poor boundaries. We had a good M. The ow somehow convinced my very smart W that she was entitled to even more than a good M.
I guess the trouble is we're never just one thing. My W was very smart, in a good M, co-d, and a whole lot of other things. In the A, I believe co-d took command.
4) As bad as I felt, I've never doubted that the WS has it worse. They have to live with themselves, even though they often pretend to be in great emotional health. But I know some of the differences between good and lousy emotional health. I know something about pretense. My W got to have an A, but I'm happy I stayed as honest as I know how.
5) When W & I were getting together, I thought our relationship wouldn't really start until we took each other to bed. Sex was absolutely the desire that was foremost in my head. My desire for sex with W2b seemed so much stronger than anything else I wanted from her that it was all I thought about.
But my real desire was for a deep emotional connection. Sex was a pathway to that connection. I didn't realize it, though. (The sad, joke's on me part is that if I had been more self-aware, I might have gotten her into bed sooner. )
I write this because I'm not sure people who say 'it's just sex' know enough about themselves; IMO, the just sex folks are probably looking for something besides the sex - some sort of validation is my guess.
6) My father was in the army when I was conceived and born. (No DNA test is needed to establish fatherhood. I look like my a twin of my brother, my father, and his father.) The people in the armed forces live through lots of pain. They had to stuff the pain or die or go crazy. Most stuffed their feelings. I glued myself to the TV from 1950-1953 watching half-hour weekly reports (Saturdays, 1 PM) of the Korean war, and the news was not always good. I still have tapes in my head of dog fights between F86s and Mig 15s, attacks with flame-throwers, 'strategic' retreats in bitter cold, etc. So yeah, I was brought up to stuff painful feelings, and I learned my lessons well.
But the feelings are in control. Always. Whether the person knows it or not.
That's part of why I have a hard time believing sex is just about sex.
7) I, too, believe men are conditioned to worry about sexual exclusivity and women, emotional exclusivity, but I also think the more objective view is how men and women treat betrayal when sex is not involved. Are their differences between men and women when betrayal doesn't have a sexual aspect? Do men and women go through different feelings when, say, a friend violates a confidence or when one biz partner betrays another?
8) My reco is to make your goals healing and making a right choice for you. We're all unique in some ways, so what works for one person doesn't necessarily work for another. Your future depends on making a right choice for you, whatever that choice may be (within the constraints of the legal system).