I'm trying to be kind, but I'm wondering why you let him fly off the handle at you? You do an awful lot for this man, with no help from his spoiled children, how is that fair? I think Jelly Bean is right, don't go for a bit and see if he decides to stop biting the hand that feeds him.
We are all going to die and for most of us it will mean failing health. But that doesn't give anyone free rein to mistreat others, does it?
Big hug!