You took the correct steps. Someone I know had two sons on drugs and were getting out of hand. She called the cops. Both were forced into rehab. One son is forever grateful to her; the other won't speak to her. But she knows she did the right thing because both are off drugs.
My son is 6 ft 4 since he was 16 years of age, now 21 and doing good.
I called the cops on my son the first day he ever laid a hand on me, about age 17, he pushed me. Get the cops in then he will know you mean business. I am assuming you do not have a 'bigger' man there. I didn't either. He left home before the cops got here, I gave them a description and sent them in his direction and they came back with him in the back of the car. They talked him through things for about 45 minutes. He NEVER laid a hand on me again.
There has to be limits and you decide what they are, in my experience if you allow drugs in you are enabling him to take harder drugs.
Your house, your rules. Tell him if he doesn't stop this nonsense, he needs to go. If he refuses, or gets violent, report him accordingly. No need for you to be scared of what HE will do. If you ARE, then there's a problem, and he needs to receive help.