You've made choices thinking you could change him, change his family, improve the situation. But I have to ask: how have you changed? You cannot change any of the other people involved in this situation. The only person you can change is you. When someone is reserved and quiet with his feelings, having a partner who colorfully display emotion will make him retreat into himself even more. I'm sure the way you act is foreign to him, too. Ask yourself why you need what you think you need from him. I realize but for your marriage you wouldn't be involved with your MIL, but how would you deal with her if he was not there? Since you know he's not going to be vocal on your behalf, how can you change your own reactions to fix the situation? It's only settling if that's how you frame it.
My husband and I started dating 25 years ago, and we've been married almost 14 years. We've had a number of major problems to overcome, things that absolutely angered me about his personality. And yet, I chose him for the things I love about him. I have learned to adapt myself to him, and I know he's changed to fit me, too. It's not perfect, but I never feel like I'm settling just because he doesn't always live up to my "standards." 'Cause I KNOW I don't always live up to his. I know I've disappointed his expectations in some ways, and I sure hope he doesn't feel like he's settling.
I don't hear you, in any of these posts, talking about your role in these conflicts. Do you feel that you've done everything you can do to make the situation better?
If you're truly unhappy and you cannot or will not change yourself to fix the situation, then leave. But don't stay with the expectation that he still might change. It's not fair to either of you.
Good luck!