I'll start by saying that you and I are about the same age Filly, with grown sons and a 30+ year marriage. And although I've never been in your situation I think I can see how you're feeling. You live practically your whole life thinking things are a certain way and then you get kicked arse over teakettle!
The thing is, he's still using you as an emotional support, the way a husband and wife in a good marriage do. But you are 'not allowed' to do the same because it 'upsets him'. The only thing you can do now is to turn off that tap. He refuses to let you vent about OW? Fine, then stop. Never mention her, it does no good anyway. You can find other outlets for that emotion. But in return he is NOT allowed to bring up his 'sorrow' about her. If he does, you need to put up your hand and say "Stop! I don't want to hear any more about your sordid little affair. I don't care about your feelings at her ending it. Why on earth would I?".
See a counselor for you and you only. Personally I'd stop going to any type of marriage counseling. Both of you are mired down in your own feelings about this mess anyway. What on earth good can joint counseling do? But getting your own counselor to help you see the future clearly and to help you work through the emotions you need to work through without any regards to his feelings, that's what you really need.
So personally, for me infidelity is an absolute deal breaker. I don't care why or how if my DH cheated, he would be gone so fast it'd make his head spin. Why? Not just because of breaking our vow of faithfulness, but because I could never trust him again. We could go to counseling, he could be an 'open book', I might even be able to forgive (probably not). But the trust would be gone and I would never choose to live with someone I could not trust.
In your situation, I'd kick him to the kerb and start to live my own GOOD life. A life free of manipulation and pain.