Sarah,
Funny, I think in my times of weakness if only I had been STRONGER, more forceful, things might have been different. (She told me that I should have "forced" her to do things with me and the kids when she refused. Of course at the same time she says I "treated her like a child", so go figure).

There is always someone else involved that gives the MLCer "permission" to act the way they are. In my case it's my FIL. He is the only person that has backed what she is doing and is now the only person she talks to about it. In most cases (like your H's) it's OW/M, usually someone they never would have given a second thought about or even noticed before the MLC. Face it, if the OP had any values they wouldn't be telling them that what they are doing is right or get involved with someone who is in such turmoil in their life.

When my W started her MLC she stopped being a mother or wife. I had to take over taking care of the kids, going to school meetings, making sure they got picked up and feed, etc. I got so involved in that I couldn't really think of my M or what I should be doing. Of course I never thought I would ever hear her say what she did on B-day. I would have been less surprised if she had told me she was an alien!

Stay strong. Keep remembering you didn't break him and you can't fix him. Use this time has a way to become a better person, learn what YOU want for YOU.