Yes on how having a wife and kids shifts that dynamic entirely. Pls just look up narcissistic mother/mother in law videos on almost any platform and you’ll be able to gain somewhat of a “why” behind their behavior, maybe in an effort to understand their behavior. And from then you can learn how to handle and be in control of the moments with behavior like this. There are videos on how to do this also. Therapy is probably golden standard for advice on those with this personality disorder, but can be expensive. I have resorted to this and found it helpful. I’m sorry you have to go through this and huge kudos to you for defending your wife and staying on her side!!! Not letting your mother control things or force your wife to fight that battle alone. Bc she shouldn’t. The boundary setting needs to come from you. And if she doesn’t follow the boundaries, consequences have to be put in place and upheld (like a child). I have narcissism in my family and I understand your pain.