I really don't have much advice for you except to hang in there until you can escape the oppressive nature of your parents. You are doing an AMAZING job that others might completely fall apart doing. You are obviously a very strong, dedicated and loving mother and your children are lucky to have you. I know what you are going though with you children because my son had autism and I am an autism teacher as well. It really sounds like you are meeting their needs as best you can. Are they in OT, Speech or behavior therapies as well? Have you looked into respite care to give yourself a break? I am pretty sure you will qualify to have experienced respite care come in if your son is receiving SSDI. I think a break and some alone time to recharge is what you need to keep on keeping (to borrow a phrase from the poem Four Skinny Trees). Sorry, I teach Language Arts, lol. That poem reminds me alot of you and your situation.

edit - feel free to pm me anytime for support.