Blue,
Set limits and expectations. If he doesn't meet them, he needs to leave. If he threatens you, call the police. Once he knows you are serious, he will begin to change or leave. Don't expect him to like the changes - he won't and will react strongly in an effort to make you give up. Make sure your wife is on board with this before you do this and present it as a united front. Also I would be concerned about substance use (based on his behaviors), especially if he has ADHD - very high co-morbidity rate with this. If nothing else, if he is on Adderall or Ritalin, he may be abusing this.
I know this sounds harsh, but he has no motivation to change as what he is doing now is working for him. Unless you want him still living at home and doing nothing at age 30, you need to start insisting on some changes. They don't have to be radical, but he needs to at least start looking for a job and helping out at home. Offer him the opportunity to go to college or tech school and let him stay at home as long as he is in school - you decide what you can tolerate, but don't let him dictate the terms.
Also don't pay his bills. I assume these are car payments, insurance etc. If he wants these, then he needs to pay himself. This will hit home when he no longer can do these things. In fact, consider asking him to pay some nominal rent.
I am a counselor and this is what I would recommend if you came to see me. By the way, my stepdaughter is 22 and now lives on her own and has a good job. She finished college at age 20. We started talking to her at 16 that the expectation would be that when she graduated from high school, she would need to go to college or find a job in order to continue living at home. She was also told that if she found a job, she would be expected to contribute to the household. If she went to college, we would support her as long as her grades were good. When she graduated and found a job, we expected her to pay her own bills and contribute to the household with chores and rent. She decided she didn't like this after about a year and recently moved out and is doing well. And she still loves us both.
Not meaning to preach...hope you don't take it that way.....and Good Luck!!
Bill Emerson LCDP