Hello. I just finished reading what you and your family have gone through. How inspiring! Best wishes to you and your son.Welcome
I don't think your mom will ever change. At her age, I probably wouldn't either, so I'd give up on that one.
I think you do need to remove yourself from the drama and do take off whatever money he is able to get from her off the top of his inheritance. My husband's family took $20k off one sister's inheritance and we knew she owed a lot more but we only found an IOU for that amount and were so happy we found that.
I wouldn't care that my brother didn't talk to me if that is the kind of person he is. He only cares about himself and who needs people in their lives like that - family or not?
Good luck with everything. You are doing the right thing!