I am so sorry about this situation Angie, and I can understand being afraid of your son.
My AD can be a rage-aholic, and it's frightening.
I have had to detach from her in every sense of the word.
Since SS mails you his checks despite you asking to be taken off as payee, I don't think it would hurt to have your doctor write a letter to SS.
I'm sorry you have so much on your plate right now.
Doubling up on Alanon meetings will certainly give you the added emotional support you need.
Take care of yourself.