Am I dumb?

Okay so I just got out of a 4 year relationship with the father of my 2 kids. We weren’t married but we was engaged. He was a really good guy but he was abusive. I can make every excuse in the book for his behavior but I know he has a problem. I left him 3 months ago but only took 1 child (long story) but I just saw him for the first time yesterday and things actually seemed pretty normal. I was hurt because he has seemed to have moved on and moved another girl in but I think that was just to make me feel some type of way. Anyway he was my best friend for 4 years. Am I dumb for still wanting to have some type of friendship with him? I mean he is a good friend and helped me through a lot of bad times but I don’t want him back as a significant other I just want him as a friend and to be civil for our children’s sake. If there is someone I could talk to that I can explain the whole situation to that would be good too.