Look, I know the hand you've been dealt SUCKS...Pain has come to pay you a visit, and you have a choice as to what you do with it: let it consume you, or push your way through it...YOU decide you want to do. But we can't make the decision for you.
I already said my piece on that one. My position is don't let it consume you because then you let the OM get the best of you.
Show him for the child he is by being the man.
Divorcing her now would give him a thrill, he would get a big ego boost to learn how upset he has left you.
The worst thing you can do to him is act as if he doesn't matter. THAT will piss him off.