Firstly, I would ignore any advice that refers to his mental health.
Advice like that is what has led to a lot of shitty behaviour from everyone from 3 to 93. Wondering why someone is treating you like shit instead of doing less wondering and nipping it in the bud. Granted, nipping it in the bud is a bit tricky when he is 18 and you should have addressed this some time ago,
However, You can try.
Do not buy in any food at all for him-get a lock for the fridge. He is earning, he won't starve. Let him buy his own.
Take his bedroom door off its hinges and put it in the garage. If you think he is capable of putting it back, saw it in half. Make as much noise in front of the gap where the door was as you please.
Remove the plugs from every electrical device in his room-you are paying for the electricity.
Do not wash as much as one smelly sock.
Ignore him-don't speak a word when he comes wailing unless it is to tell him to fuck off.
Try this approach. It may not work but it has a better chance of success than pandering to him. You're in charge. He has treated you like shit. Return the favour with the added power that it is your house and he is only in for as long as you say he can be.
Or you can wring your hands, wonder how you can stop him behaving in this way, address his mental health and make life misery for yourself and the rest of his family.
If you choose this approach get thee to to a local tattooist and have Walk Here stamped on your and your husband's foreheads.