The solution to this whole issue is for the man to man up and start stand up to his mother and saying what's important to him whenever there's some kind of conflict so that he can learn to side with you in the relationship rather than with his controlling mother.
There's really nothing that you can do as a partner in terms of what his mother does, and the solution to the problem is not for the mother to change her behavior. You can't expect other people to change, and we have really no control over other people's behavior.
The only influence that you really have in the situation is influence with your partner where you can say, "Hey, if you don't stand up to this woman and start acting like a man around her and do whatever work you need to do in order to do that, then I'm just not going to want to be around you and I'm going to be out of here."
The relationship is not going to work if a man is continually under the thumb of his controlling mother. So essentially what I'm saying is that you need to be pretty firm with a guy who has a controlling mother and make sure that this issue is on his radar so that he knows that he's got something here that he needs to go and deal with because there's no point in getting into an argument with his mother, with your in-laws. It's just completely counterproductive.
The man has to be the one that stands up to his mother because every mother is ultimately waiting for the day when her son grows up to be a man and starts living his own life so that she can actually relax, kick back and start to enjoy her retirement or whatever it is that she goes on to do with her adult life without having to worry about him all the time.
Now, you can't do that for her. Only he can man up and start saying, "Look, mom, it's unacceptable for you to do this," or, "No, I'm not going to do that."
One of the best things I ever did with my family was to one year just take off and not even turn up to family Christmas. I got on my motorbike and rode up the coast of Australia and had a fantastic time, and I noticed when I got back that my mother's attitude towards me had changed. Rather than Christmas being this really big deal like it had been, she was a bit more relaxed about the whole thing now and I'm pretty convinced part of that was because I stood up to her by saying, "Well, you know, this year I'm doing my own thing."
A man with a controlling mother has to do the same thing; he needs to learn how to do his own thing, and what you can do is be there to support him in doing that because it is going to bring up a whole lot of anxiety for him and a lot of fear that it's important for him to work through because this is the process that is called growing up.
By doing this, by separating from his controlling mother, he gets to be a man and you're going to find him a whole lot more attractive and more fun and interesting to be around once he's able to be with his mother and treat her like just another woman, rather than being this kind of controlling negative influence in his life.
I know maybe some of this has been a bit hard to hear because if you're in this kind of dynamic with a man who has a controlling mother, what you can actually do about this is a bit limited. It's really limited to what you can do in terms of relating with your man, and another telltale sign of this is that if this is a topic that you find difficult to talk to him about it's probably because he doesn't really want to talk about it and simply avoiding it is not going to get you the result that you want.
It's time for men with controlling mothers to stop avoiding the situation because that's exactly what keeps it perpetuated. So what I recommend you do is take some time when you're both in a calm space when you haven't been arguing or whatever if that's going on and say to him, "Hey, there's something I'd like to talk to you about, and I know this might be difficult but these issues with your mother are really causing me some grief," and talk to him about how you feel about that.
Because if he is concerned about you and loves you and cares about you, then he's going to want to know how you feel and it may not be comfortable for him to hear this, but the way to motivate a man to get him to address this issue is to be really straight with him about how it's impacting you and make him aware that it's impacting you in a negative way. And then if the relationship is important to him, then he's going to be motivated to want to act to deal with his issues with his mother so that he can have a good relationship with you.
Now, if he's not motivated to act to deal with his issues with his mother so he can have a good relationship with you, then that's a sign that, I'm sorry, but it's time to go. If he doesn't care enough to really want to take this on and deal with this stuff so that he can relate well to you, then he's not the kind of guy you really want to be around. And that's the hard word.
So that's my tip: be really straight with your man about how issues with his mother are impacting you. Don't try to deal with the issue with her directly because that's not likely to work. It's really him that has to stand up to her, and you can be there to support him and help him to learn how to do that in a way that's constructive for everybody.
Also, I recommend that you point him to the article that I wrote on this topic of How to Recover from a Controlling Mother, and that'll probably give him some insights into why he feels so anxious around his mother and what he can do to start moving forward so that his whole life can be better. It's not just about the relationship with you; it's also about a man becoming able to be himself in the world which is very important.
For a man to be truly confident he needs to deal with this mother issue. Point him to the article and then see where you go from there.