I'm sorry your mother is going through what she is, but what I do see is a mom with 2 Autistic kids and trying to do everything herself, but she does have you and you are you source of strength.
My son gets tested for his mild Autisim this summer before he turns 18 and I can't do anything else to help him.
I don't see how he was being a jerk to her by telling her to go lay down and try and relax a little. Autistic kids usually do quite well by themselves playing in their room. I did say 'usually'.
My son is an awsome person. He likes to play computer hand-held games and can pretty much take care of his own needs now, eventhough he does need reminding...lol
How old are the kids?
Her hubby should be taking care of them also when he's home.