Of course in_it is the wronged person here and shouldn't have to put up with H's crap. That's really not the point. She has expressed a desire to keep her M together and is looking for advice on how to do that. AS is just trying to help her with that.
It's easy to defend the wronged party in a disintegrating marriage and villainize the other person. Most friends and family do that, and DR points out how they think they are helping "their" side. They won't have to live with the aftermath. The ex-spouses will.
So in_it, please keep DB if you're up for it. It may help your M, and it will certainly allow you to feel you followed a path you can be proud of.
And notice how he again pulled you into an argument. For whatever reason, he is still hooked on telling you he's leaving to get a response out of you. I know this is repeating, but that's codependent behavior, and lovingly detaching is the only good way to deal with it. I think you're doing great, just continue developing strategies to not get drawn into these arguments. He's in a real fog right now.
H: 38 xW: 38 M: 16 T: 18 S: 9 BD: 2/2012 W moved out 4/2012 D: 11/2012