BQT, I just finished reading a book titled "He's Scared, She's Scared" by Garter & Sokol, about commitmentphobes and their relationships. Now, I'm not saying necessarily that your H's a CP, but check that book out, because I found that it gives insight to a lot of what WASs do, and it may be because everyone has some degree of commitment phobia that they act out. What you've been describing is very much symptomatic of that.
For example, H's being hostile to you, and his starting baseless arguments with you that are about your "flaws", and his going out on his own, are all ways he's creating distance for himself. The more you try to get him to draw closer, the more he'll create distance.
That's what's happening with the OW from what you describe. He's apparently distanced himself from her now, and she's responding by pursuing. She's going crazy because it had seemed to her that they were so deeply connected on so many levels, that his now not wanting to be around her is unexplainable to her and she thinks it's her, and she's stepping up her pursuit by declaring her love for him, which she feels more acutely because of the pain of loss she's experiencing. IOW, she's acting like the typical LBS. But you know that behavior will continue to push him away.
He probably is missing her somewhat, for when the distancer/CP is out of the relationship, their phobias are no longer being triggered by that person, so they tend to reflect on the things they liked. But more accurate is to say that they are always carrying a conflict within themselves, always doubting if they're doing the right thing or not, always on a fence. He's that way with her, he's that way with you.
You have two real options only. The first is to end it with him. Totally. Free yourself.
The second option is to deal with this personality by distancing yourself and staying distant, dropping the rope completely, not drawing close to him, not planning to do things with him, living your own life, no ML, no "ILYs", no incluing him in anything you do... and all that will have him likely draw close to you again, but be aware you're still dealing with the same man with the same issues, so if you respond to his drawing close by you drawing close, seeking intimacy, he'll only distance himself again. When he draws close though, you can start pointing out these phobias of his, asking him to reflect on why he has this problem, and hopefully, since he's probably aware that he has some issues, he'll seek to do some work on himself. If he does not, just end the relationship for your own sake, move on. You'll find a better love.
