You and H are in the hard part of his ending it with her. It's a tricky balance. While you have to do what OT is advising about setting limits and being clear, you also have to ignore any bad behavior.
In my case, I'd set limits and then he would go deeper underground with her. Don't get too scared, but I started questioning at Christmas and it wasn't until June that I found out the entire truth. I ignored from DEC-APR and then started stating I was uncomfortable with their R. During the time I was becoming more vocal, they heated up. However, I maintained my stand that I wanted us and she could not be in the picture. My H was her boss and I had to watch him leave every morning. It killed me every day. You can read about my sitch in MLC section. My outline is in Keeping Love Alive section. I won't say more here.
I had it in the back of my head that I was not going to play second fiddle. I finally did issue a LRT because if he wanted her, I didn't want him. She may have been young enough to be our daughter, tall and thin, but I knew what she really was inside. Anyone who would take up with a married man, and any man who would do that to his family was not someone I wanted to be with.
It's so hard because it's like something comes in and snatches your H's soul and you don't know him. I needed the real one back and was willing to let him back, but he had to choose. I knew I had to give him some time, but I also had a timeline of my own. I think it was my willingness to give him up that gave me strength.....and that strength came and went.
M 55 H 58 M 24 T 29 S 22,21, 19 Bomb 4/10 It (A) really isn't about you 11/2013 We all have work to do
The truth will set you free, but it will almost kill you first.