I’m sorry you are going through this.
You already saw the red flags. I kind of think it’s not only a matter of alcoholism. I rather think alcoholism is only his way to get high and get excitement. I see more red flags than his dependency of alcohol.

For me is also very difficult to get away from people I care but you can do it.
Try to think it’s gonna be very hard but the suffering will end up. The ideas I pop into is look for support on other people around you that are positive for you, spend time with them. If you feel confident with someone of them or even a therapist, tell them what’s happening and what you need from them. What you are trying to get, that is, zero contact with this person. Focus on activities to keep your mind busy.
Think that many times, leaving a romantic relationship behind is so hard as getting free from an addition. What for your SO may be getting free from alcohol.

Sure, you’re going to get more ideas.
Wish you luck!