How do you break up with someone you care about?

I'm 25.. I've been dating a guy I've liked for a little over 8 months now. It's been an extremely toxic relationship. He drinks too much and yells at me, I'll drink too much and yell at him back. He's 27 and always broke.. I could go on. I miss thinking of the person I thought he was. Before I got with him, I told him I just wanted to be single but he really wanted to date me so I figured I'd give it a shot.

He's been staying with me and sometimes his parents house. He's about to move in with one of his friends.. We almost break up every weekend. He'll make long terrible Facebook and Twitter posts about me.. I care about him as a FRIEND. I'm not sure how to break up with him without hurting him. He's waaaay too in love with me but he's so codependent and just drains me of my happiness..

I'm thinking I'm going to wait until he moves in with his friend to break it off. I'm going to make sure to do it when both of us are sober. I'm not quite sure exactly how I should do it.. any suggestions and other advice is welcome.