It's one thing to be polite, quite another to put up w/ abusive behavior. I wouldn't stop being polite and considerate, etc. ordinarily. But if someone is rude or hurtful, please call them out on it. Even just a simple, "What could you possibly have meant by that?" might suffice. H's cruel "joke" should have been met w/ the silent treatment or something of that sort. No matter if he expected you to act as if nothing happened. He needs to know he can't have that.
But mostly, I agree you need to develop a life outside of him and a circle of good friends. Also, I agree you need to seek legal and psychological counsel - w/ the aim of getting out of this situation. Please remember, also, we're here for you!
Meanwhile, my deepest condolences on the loss of your dear sibling. Also, sorry about your parents' dementia. And very sorry you are in this abusive situation. Hugs!