Do yourself a favor and don't mention the A again. Trust me on this one.. it will be the most positive step you can take with your H and M. Can you look at it as a gift from you to him? I understand how unfair it feels.. I've been there. But really, not talking about OW has been a good thing for our R. In fact, she doesn't exist in our R unless I'd be the one to bring it up. That's a gift I'm giving ME. Good luck!
I'm reading the Dance of Anger.. author is Lerner. It was recommended by someone on piecing. Very good book about breaking cycles and dealing with anger effectively. It's helped me to take responsibility for my anger and to not let it consume me. It helped me to see how the cycle of dragging H into a convo about OW was an ineffective way to communicate. I'd ask him about it to determine how much he loves me vs how he felt about her. Well, now I just concentrate on how he feels about me and if that's getting better day to day. Using his feelings or experiences with someone else is just not a good, useful yardstick in our M. He feels how he feels about me.. as long as that's getting stronger.. we're making progress!
