You might be overreacting; it’s hard to know. Some kids go through developmentally normal pushy phases that soon work themselves out; other times, today’s preschool shoving turns into tomorrow’s out-of-control punching.
But the penalty for overreacting is a lot milder than the penalty for under-reacting when it comes to aggressive and perhaps violent behavior in young children. Talk with his pediatrician out of his earshot and get the name of a behavioral specialist – hopefully a psychologist – with whom you can get a consult.
But don’t view your child’s genetics as destiny. The way you raise him (and that, of course, includes how you let his father influence his life) will likely be far more important than his DNA in terms of his behavior.
It sounds like you can understand your husband’s perspective, and you might want to get away yourself but feel guilty about that. But what’s the history here, and where’s the middle ground? Have you ever tried drawing more boundaries where you are? Have you tried to get her into treatment, or better treatment?
This isn’t about geography; it’s about whether you’re willing to prioritize your marriage and stand up for your partner – and how you plan to handle a parent who’s not well. Talk with him about what changes you are willing to make to stand up to her. Here. Now. And if you can’t do it, then be willing to get help in trying.