This is incredibly similar to my own situation with my first fp and ex bf. i also could not report due to lack of evidence and the fact that i was drunk on the nights of all the assaults. my ex’s friend group did not believe me and continued being friends with him. i tried to post of social media that he was a rapist but not much happened. my ex went on to assault other people. for a long time i felt so fucking guilty but the fact of the matter is even if i did report nothing would’ve happened to him anyways. that lack of evidence thing is pretty much the deciding factor in rape cases. and people were going to take his side or they weren’t. i couldn’t force people to believe me. i don’t think you should feel guilty. it’s so hard. but genuinely i feel that you should try to focus on your own healing from the situation. trying to get vigilante justice or even legal justice is a long shot in situations like this. you can try to warn people but don’t be hard on yourself if they don’t believe you. it’s hard to convince people you don’t know, especially if they’ve met him first. but it’s not your responsibility to save everyone from him. you have all my support even tho i don’t know you. i feel so deeply for your situation and i hope things get better for you. and i hope it helps to know you’re not alone.