WOW! I know what you mean about loosing respect for him & if you can get it back. I think that is where both of you need to go to IC & also MC. If he is wanting revenge, that is not good either but maybe that is just his anger coming out & he will finally get over it. I do think he needs some help with that, did he say how he wanted to get revenge?
I'm glad you are trying to talk sense into him b/c she is not worth his or your time anymore. He has already wasted enough time & energy on her.
I know you are in a bad spot right now, you have been so strong you keep hanging in there. I'm glad you & H are talking openly about all this b/c I think that is what needs to happen according to everything I've read. You do need a good MC.