Hello!
From my experience, I also stopped using alcohol numerous times for varied periods of time. I had the misconception that I could control my drinking, so after a few months sober I went back. It only got worse, and my abuse became progressively out of control.
You have to do what works best for you and him. If he fully accepts he has a problem, and he comes to the realization that he can’t drink, I believe anybody can have a second chance. But, statistically speaking...relapsing is a high probability for any alcoholic. It takes many of us years of going on and off the bottle to realize we simply can’t drink, and refuse to ever drink again.
I work around domestic violence / assaults every day. Additionally, my father was an abusive alcoholic. It’s a scary situation, and I know alcohol is a direct correlation with the behavior.
Staying or leaving is ultimately up to you. Nobody can tell you otherwise, but as you know..alcoholism is a disease. It’s not easy to beat. My father was given an ultimatum (family would leave him), went to treatment, and has been sober to this day. Sobriety is very much possible for your guy friend, but the process is slow and may take some serious assement by you.
Good luck, and I pray he stays sober for both himself and you!