Welcome to SI, the best club you never wanted to join....
Your H's insight that he was trying to fill a void is a good start. IMO, he needs IC with a good IC to figure out how to fill that void himself. That's the only way he can change from betrayer to good partner.
MC may help now, but in MC the M is the client, and the M didn't fail. your H failed the M. IC for him is the only way for him to lead a morally and emotionally good life, and that's the only way for him to be a good life partner. ('Good' doesn't mean 'perfect.')
For me, my W's A started as if I was being run over by a steam roller. As low as I already was, d-day, started me on a roller coaster downward into despair. I felt awful for months.
In other word, how are you doing emotionally?
From what you write, if your H is honest, R may be possible. It may be shame that's keeping him away ... or he might feel so bad about himself that he can't imagine anyone wanting him. OTOH, he could be playing you.
The only way to find out is to communicate and trust your gut.
The key to R is honesty. You need to ask your questions, and he needs to answer them. He needs to volunteer information about what he's doing and who he's with. He needs to get non-defensive and be with you when you need to vent. He needs to participate in defining what your M will be.
If he's not a candidate for R, so be it. As awful as you probably feel, you can survive and thrive without him. So have some faith in yourself.
I'm not sure you need to expose the A. I didn't generally expose my W's A except to her supervisor. That was a big expose in terms of consequences, but we've always been pretty private people, so friends don't know.
Your H might confess to his boss, in the hope of minimizing contact with ow. I agree - a new job for one of the aps is necessary.
IMO, an NC message should be very brief. My W went NC via text message on ow's birthday. (I've heard people complain about being dumped via text, so I liked that method.) In any case, there's no need to show respect to the ap.
I suggest browsing in the forums, and in the Healing Library - https://www.survivinginfidelity.com/faq.asp.
[This message edited by sisoon at 10:07 AM, May 23rd (Thursday)]