Hi MTP. I remember reading your first post in JFO and wishing I could reply to it. So much of what you describe reminds me painfully of the months after my A.
I had feelings of love for the OM, and while I ended the A voluntarily, I refused to go NC. It wouldn't have been complicated to do. He had moved to the other side of the country. I told him before he left that both the romantic and sexual aspects of our relationship were over. And yet, when BH said he needed me to kick OM out of my life completely, I told him no. It seems baffling when viewed logically. Why would I spit in the face of a suffering BS who was offering to reconcile for the sake of an ex-AP?
One of the challenges of analyzing a WS's behavior is that we deceive ourselves about our motivations as effectively as we deceive everyone else. There's a mess of truth and lies mixed together that can be hard to unpack.
OM and I started out as friends, and when we began developing inappropriate feelings for each other, I was conflicted. I felt scared. I felt powerful. I felt desirable. I felt grateful that he had anesthetized my fear of inadequacy. And I felt responsible for him, because he had been hurt by someone romantically in the past, and I was going to hurt him again when the affair ended. I had such deeply internalized fears of abandonment that rejecting someone felt like the worst thing I could do to them. Cheating, in my mind, wasn't as bad, because it was something I was giving from my own heart and body that was mine to give. I truly didn't consider that I had promised those things to someone else and was gifting stolen goods.
I'm sure there are plenty of WS who do the math on D-Day and dump their AP without a backward glance. I believed it was wrong to encourage OM's vulnerability and then throw him on the trash heap. Anyone with sense in their head would be more worried about the vulnerability of their BS, but I reasoned that BF would be ok because he "won." I picked him, ended the A, and broke OM's heart. Under that logic, the least I could do was honor my promise to stay friends with the guy I jilted.
This narrative conveniently helped me ignore how important it made me feel to have two men battle over me. I pretended to myself that it was over even though I knew OM was still silently pining. It's standard romance novel bullshit, but I ate it up. That's one of the reasons we encourage BS to detach. It's not the most important reason (which is self-protection from a person who has proven themselves to be emotionally dangerous), but it also reminds the WS that security is no longer owed to them. After betrayal, the responsibility is on the WS to prove themselves worthy, not the other way around.
Like you, my BF was afraid to detach because he didn't want me to run to OM's arms. Unlike your WW, I always knew I wasn't going to. In the four months of the A, I had seen that OM and I would have been a disastrous long term pairing. I just refused to accept that any contact meant the A was ongoing. Waywards have a hard time believing that we can't fix what we did and/or avoid the worst consequences of it. Because we have such broken moral compasses, we can head off in the wrong direction even when we try to go in the right one.
My bullheaded insistence harmed my BF (now H) terribly. It didn't help OM, either, because NC was inevitable. Staying in contact just gave him false hope and kept him from getting on with the business of forgetting about me. It probably wasn't as hard as I imagined, either; WS and APs are pretty good at looking out for themselves. But whether he was deeply attached or not, a clean break was still the right answer.
You have one bitter advantage that my BF didn't. I refused to admit the full extent of the EA/PA. The truth your wife gave you is brutal, but at least you know what you're working with and can decide if it's a deal breaker. I denied my BF that agency and told myself that the details I was hiding were inconsequential. BF knew OM and I slept together, he knew we exchanged ILYs, so I rationalized that he knew the worst and could make his decisions based on that outline.
All these toxic choices fucked with BF's head. Although I was sympathetic and gave him lots of hugs and reassurance that the A was over, I expected him to decide whether or not he could forgive me without even telling him what he was forgiving. I used my resentment about NC to develop entitlement about reconciliation. Because I gave in on BF's most important demand, I thought he owed me guarantees in return. He was so relieved that I agreed to go NC that he complied. He rugswept and ignored his gut feeling that I was still lying. Eventually, though, he couldn't pretend anymore, and that's how we ended up back here when OM and I haven't spoken for decades.
As far as how long it took to stop having feelings, I don't remember exactly, but the NC helped enormously. I went years without thinking about OM. In times of stress, though, when I was feeling inadequate for some reason, I still romanticized the memory of the A. I didn't wish I had chosen differently, nor did I relive the sex, as most BHs seem to fear. I mostly forgot the sexual details. Instead, I fed off the memory of being wanted and irresistible the way a former high school football hero lives in the memory of winning the Big Game. SI helped me to see that the OM was just a source of validation. That doesn't mean he had no qualities that were genuinely attractive to me, but what really sold me on the affair wasn't what I saw in him, but what I was soothing in myself. Once I started examining those psychological wounds, I was able to see OM was just a band-aid.
I'm glad that you're pursuing therapy with counselors who are trained in infidelity and trauma recovery. Don't rugsweep. Take all the time you need. If your WW can't support you through that, then you are better off going it alone than making promises you are in no condition to make.