SRI, in your last post you listed several questions you are nervous about him asking his IC. My thoughts are, if he has any or all of those questions, wouldn't you WANT him to address them with someone? Your fear seems to be that even has those questions, but you can't control if he does or does not. NOT going to an IC doesn't mean he doesn't have them.
Whatever his desire for IC, I believe you should support it wholeheartedly. I only WISH my WS wanted to go to IC. He went to MC with me a handful of times, but neither of us felt it was helping us much at the time. Yet I have since begun IC and have all along been the one doing pretty much all the work to fix things. I had to actually pack a bag and leave just to get him to read a dang book. Not that he's not "trying". But his way of trying is moving on, loving me the best he can, and trying to forget the past. Just last week I tried to encourage him to talk to "someone", an IC, a friend . . . someone he can talk to on an ongoing basis about stuff he's going through, frustrations from his past, his present, whatever.
I think the fact that your husband is working so hard on many levels to fix things, to fix himself, to keep his focus on a happy and healthy relationship with you is amazing. And it sounds like he has a list of horrible roll models, so it's seems clear why he may feel he needs more support, advice, guidance, etc.
When I first read that his last IC knew he was having an affair I was initially appalled . . . until I remembered that counselors are bound to client confidentiality. I don't know the specifics of that whole situation, but I would imagine his IC was trying to get him to leave that extramarital relationship. And yet if he didn't, maybe that's part of why you're so worried, which would be understandable.
I asked my counselor if she does couple's counseling and she said at her office they have a different kind of system. The wife goes to an IC there, and the husband goes to an IC within the same office, and when they do MC the four of them come together. That way, each spouse has a sort of "advocate" who understands their point of view and can help guide the conversation. In these cases, the two counselors also share important information with each other that they feel each other should know.
And when I filled out my forms to see my IC, I listed the name of the MC my husband and I had seen. She had mentioned that if we were still seeing him, she would possibly confer with that MC on occasion as seemed necessary, but I believe it wouldn't be without my knowledge. Or at least I'd sign a paper in the beginning allowing her to speak with him at her discretion.
Maybe this can be the case with your IC and your husband's IC, even if they are at different offices. Ask your IC about this and then if he/she agrees, see if your husband would be willing for his IC to speak to yours, etc. They don't have to share everything and may not feel the need to share any information with each other at all. But maybe it will put you at ease if you know there aren't any secrets you "should" know about.
Now, having said that, since part of the whole point of IC is privacy and confidentiality, there may be some things your husband wants to share that he doesn't want you do know, and yet they don't have anything to do with an affair or anything of the sort. They just may be things he's having a hard time talking to you about and needs to discuss them with someone else who may bring him around to a place where he can talk to you openly about them.
At any rate, I'd encourage you to "let go" and let him get the IC that he feels he needs.