Your son is spoilt. You have spoilt him. I'm sorry, but that's the truth. You take exploitation, emotional blackmail, manipulation and abuse from him, which teaches him that's how to treat women.
You are teaching your son to be an emotional abuser. Right now, you're his victim, and your poor DH. Of course he can clean a fucking floor. Of course he can eat with the bare modicum of acceptable table manners, so others can enjoy their food too. He doesn't want to because he is completely selfish.
He has a fantastic deal with you. A grand a month pocket money, and he abuses the people who enable that? At 22? Dear God.
You owe him one thing: to tell him to leave, that he cannot abuse you any longer and he has been given chance after chance. He treats you like dirt because you have taught him to do it. Stand up to him! He can't respect you because you don't!
Your son will leave at some point, when it suits him. That's inevitable. Do you really think he'll visit you much, if he treats you with such contempt? Kids grow up and leave home and build their own lives and that is as it should be. Your DH is the future, and you are at serious risk of jeopardising that over a 22 year old who holds you in contempt. Stand the hell up for yourself, for your marriage, and for your future. Or you may find that future is a lonely one.