Mental Health Support

Pete Walker's C-PTSD book might be of interest to you.

I hesitate to suggest this but have you considered the possibility that your grandmother may have similarly abused your mother? That might explain her inability to be a mother to you. Even if true that wouldn't excuse the way she's treated you. But maybe that can help you find some peace with the estrangement. You're not the problem. You are, in fact, pretty cool. If your mother doesn't get that it's her loss.