Lost, I'm so sorry for your fear and your pain. It feels very familiar.
Albatross is 100 percent correct. They are choosing every single day how they will act and what they will do, and then they expect us to pick up the pieces and deal with THEIR consequences. The sooner we can start learning how to stop doing this (and it takes time, even for the strongest of us), the better off they will be and we will be, in time.
Lost, you know you can't have a violent drug abuser in your home. You have another child. You have a right to peace and a safe home and a place of sanctuary so you can go to work and take care of your family. Someone/anyone who disrupts this---for me my last straw was when my son stole from me---is gone. Now.
Your son needs help. He needs professional help that is way beyond what you can give him. If he can't/won't get that, he will likely end up in jail. That's the other option, most often. My son went to rehab multiple times---every time he resisted it 100 percent---and he was in jail 8 or 9 times. Finally, the last time he got out of jail, he was done with himself and his way of life.
This was not on my timeline. I can't believe it took him nearly 6 years to stop using drugs, selling drugs, breaking the law and doing all kinds of wrong things. My rock bottom was years before that. Every time something would happen, I would think: this is it. NOW he is going to turn around, surely. Didn't happen.
Your son is a grown man. He is going to make grown man choices. He needs to live the grown man consequences of those choices, whatever they are. That is the ONLY way people change, ever.
We know how very painful and hard and soul-wrenching this is. I had to completely change the person I was in order to get through this. That took time too. Through therapy and Al-Anon and having a sponsor and working the program and prayer/meditation, exercise, so many different "tools" I used during that time, I was able to change and become a better person (a side benefit I didn't expect!). I was trying to just merely survive.
Please keep sharing here. You need to do what you can live with. Let that be one of your mantras. We're here for you.