I think a parenting forum is an excellent idea! My son has many of the same issues as yours, and a couple of years older. I am relieved however that he does not have these anger and disrespect issues. He did for a brief time when he was placed on prozac to compliment his ADHD medication. Suddenly this caring, sweet, respectful boy turned into a demon. Luckily, once we took him off the prozac his personality returned to normal.
I'm sorry for the issues that you and your son are dealing with. It sounds as if he's seen a lot in his young life and does not know how to treat you. Here, our son's disabilities were never an excuse for bad behavior and he was expected to act accordingly.
I'm no expert, but my son went to a camp when he was younger with many other young people like him. Many of them were on disability, is this available to your son so that he may get the insurance coverage he needs, thereby getting the help he needs?
I've concidered looking into this many times for my son, while my husband and I can support him financially (work is difficult for him, he also suffers from anxiety as well), I am very concerned at times about his lack of insurance.
I understand how difficult this choice is for you. On the one hand you have a disabled child and you want to protect him, on the other he's an adult and does not respect you or the rules of your home. If he does have another place to live where he will be cared for and will not behave this way, then perhaps its time to look into that option very seriously.
Good luck! I hope for both your sakes you are able to find a solution to this problem and I look forward to finding out what you've done and how it is working out.