Here are my thoughts here, so take them for what they are worth…
The suggestions to be blunt and straight-forward are excellent. Bill’s conversation is one that should take place, as should the simple question of “what have you been doing to strengthen our marriage?”
Face-to-face is a must and I would have you write everything down. Who cares if you have to use it as a reference b/c this is important to you and you don’t want to miss out on the opportunity to speak from the heart.
I know you've said them before, but the problem is he hasn't listened. You can say them again and ask for a response - a letter may do the trick. A non-response from him is also an answer and although he's doing it to you now by not writing back to your letter, it still seems to be a good, direct, blunt way to let him know - "either get w/the program or the train is leaving."
That said, I do firmly believe IC can and will be your friend if you C will challenge you to be better by looking deep w/in yourself before looking elsewhere. If you haven’t asked for this already, I suggest you tell you C to challenge you – even though it will be difficult and sometimes painful – b/c that is the only way you will grow and find yourself.
Remember “to get through the pain, you have to go through the pain.” I’m referring to you personally, not H. He has his own journey to take (and quite frankly, I’d demand his going to IC as well) as do you both still as a couple.
However, until you come to find peace w/Maria, nothing will be solved for you, your marriage, or your H.
FG says “do work” and I think the M should be set aside right now to let Maria work on finding Maria – truly digging and unearthing to find Maria. After that, everything will fall into place b/c Maria will truly and completely know who Maria is and what she wants out of everything.
Again, take my comments for what they’re worth, but from my seat, this is how I see it.