Ex best friend & Ex boyfriend dating. Advice?

Well it wasn't REALLY bothering me till just recently so here it is. I am really good friends with my ex boyfriend's friends (whom he barely sees because he has conveniently pissed each and every one of them off at different times) to a point all of us hang out every 2-3 days. My initial plan was to cut all ties but they were very consistent on hanging out to a point where they don't refer to me as their boy's ex but just as their friend. They never bring them up but I recently bumped into my ex and he started to make a scene in public when I wasn't even talking to him. It was because I got so pissed about finding out about them that I slept with HIS best friend a couple of months ago. He had known about it the second it happened but for some reason acted out the time I recently saw him. Long story short both of us ended up getting really fucked up that night, and I have him on blocked list so I don't know what txts he sent me or whatever but he ended up storming in my apt through my window and all of that yelling and anger lead to us somewhat hooking up till the moment I sobered up and kicked him out. He still talks to her and she at one point swore off him and stopped talking to me because of him because she had a stalkerish like crush on him from like 8 years ago even to a point where he would be creeped out by me even mentioning her. He knew how hurt I was when she stopped talking to me bc of him and even after whatever I went through for him, he broke up with me and went to her. This guy is kind of always looking for the next high in his life.

Any advice on this circle jerk from hell?