You're right about the OM. I wish he would do something to her that would just see him in a bad light once and for all. I even found out that he was already cheating on his W the same time he tried to cheat with my W. So he had 3 people. After I told my W, she said it didn't matter. That's how hung up she was on him.
Stuck, I haven't followed your sitch, but what you wrote here doesn't surprise me in the least.
Since I've been involved in the sitch that no one wants to be in, I've learned a lot.
And there are a very good number of sitch's like this where one or the other of the cheating spouses is in it for what they can get and the other is "in love" and could care less what the OP has done in the past or is doing currently. Our spouses feel good when they're with the OP. Doesn't matter if they have another BF/GF they're cheating on their spouse with while they're cheating with your spouse. Whether its a temporary thing or an actual character flaw with our spouses is the question that needs to be answered to determine if the marriage can be saved or not.
In my sitch, my W is not a cheating person. We've had a pretty darn good marriage for 22 of the 24 years we've been married (she even admits this). And then W had some major stresses, grandma passing away, relocation for work, mentapause, all adds up to the perfect storm of an A. And the OM in my sitch is a serial cheater. He was scr*wing a woman that my W works with and when she transferred he had to find his next mark. W was it. My W knew he'd cheated on his W multiple times prior to the beginning of their A (she told me this recently).
OM moved ~200 miles away and almost immediately found a new GF, and my W had a pretty good idea about that too, but my W was still ready to D me and thought OM would marry her (after divorcing his W) and they'd be one big happy family.
I've recently come to grips with the fact that there's nothing we can do beyond GAL and becoming the person no spouse would want to leave. Busting the A works in some cases (It gave my marriage it's best chance), but that draw Sandi and others talk about is so strong that it will cause an otherwise rational, moral person to be willing to throw everything away because of how the OP makes them feel. They are convinced because they either have never felt that way with you or it's been a long time since they have, that the marriage is no longer worth it.
From your post, your W and my W are in much the same place. I don't know how long you've been at this, but it will take a long time. It's been over a year since (from what I can determine) the A officially ended in W's mind (my adult kids put a little crimp in her fantasy land) and there have been glimpses of my old W from time to time, but up until a few months ago, she was still so foggy that you never knew what you were going to get on a given day. Just these last few months I'm seeing the real her more and more. Still not wearing her wedding rings and still hasn't said "I love you", but you're spot on with your observation on the transition state and her being emotionally empty. My W is right there.
Will we get there? Don't know. Most times I feel like the only way we won't make it is if I give up, but that time is coming. How much can a person give without getting what they need in return? And that's the crime in all this. Many times the LBS becomes the WAS and then the original WAS figures it out and it's too late.
Patience. Never knew I had this much Patience in me.
For what it's worth.
Hope4us
Me - 49, W 49 S22 & S18 Dday 9/4/07 W claims NC 4/7/08 8/29/09 - Divorce Busted. Lots to work through, but we're going to make it.