Well, I can think of a lot that you can do, but the question is, are you willing?
First off, illegal activities are going on in your home. You can be charged as an accessory for knowing and not doing anything about it.
It sounds like your situation calls for drastic measures. If I were you, (and this is just my opinion,) I would see if there is someone you can talk to in law enforcement, in social services. You need to know what your rights are, where the law stands and what can be done. CAN they make him go to the hospital? WILL they let him out of a mental facility after a few days?
I would also tell someone that you THINK drugs are being delivered to your home and how to handle that legally.
He's in your home. You don't want him. He's trespassing unless he's married to you. Start talking to people, anyone, to get information.
Save up to move.
Document EVERYTHING. Write it down in a journal. Everything he says, does. Every time he threatens himself. Keep a written record. You never know when this may come in handy.
If you have a friend you can trust, you can start boxing things and moving them out a little at a time. You can get out. You know you can. Just start to plan it and move in small steps.
But, the big question here is, even if he does move out or even if YOU move, are you going to let him back in your life again? If so, then all of the above is 100% pointless.
If you're asking how to cope with him staying with you forever, you have to live your own life and set boundaries and be ok with him on your couch for a very very long time (unless he really does get help, but you'd be waiting on him.)
Good luck with it all. I hope you find your answers. Until you really decide to sever your ties, then leaving or forcing him out is just temporary. Figure out what you want permanently in your life and stick to it.
There is no way on God's green earth that I would ever allow people to buy/sell drugs in my house. I would call the police every time someone came over to sell something. Lots going on here that is disturbing.
You don't have to give him money.
Turn off his cell phone if you're paying for that.
Get rid of the landline if you're paying for that (and get a cell yourself,)
Turn off things like cable/satellite/internet.
Is he living in a hotel with you feeding, bathing, paying for his every whim? Are you a maid? A servant?
Ask yourself these things. What life do you want to live?