Hard to deal with inlaws on this subject in particular. I didn't have that problem as my husbands parents shut him out immediately, and they had no contact while he was actively using. Took his mom many months after he went through rehab and all that for her to reach out to him again. I had my own issues with her behavior, but knew that she had to take things in her own time. So, I can only wish you luck with the parents.
In my post I was not talking about NA meetings. I was talking about 1:1 professional therapy, so he can really dig into his issues. I cant tell you what is in your husbands mind about "meetings" but I do know that it was not a route my husband wanted to take because yes, he felt it was not healthy for his mentality; constant reinforcement of addiction, he felt it would make him feel stuck. He used rehab based on private therapy and then continued with a Dr. when he came home. It worked out well for him so far (just over a year clean). I worked with a private therapist too; she was an incredible help to me. Glad to hear you have that support.