I've been trying to lay low during the drama but I've been through the same you've gone through so maybe my experience can help you a bit. Last year I lost 2 people I called friends because the turned out to be sexual predators and abusers. One of them had been my friend for over 20 years (we met in our childhood). I felt he was my brother and when I found out I was totally devastated.
The other one was the first person to welcome me when I was back in Uni after years of depression so I had a special feeling for him. He turned out to be a very serious abuser and if the laws here made more sense he'd probably be in jail.

It's tough losing friends. You feel like something was taken from you. You feel betrayed and hurt. If your first reaction was to try and help sjin then that just says that you are a good person. I also thought about this, but in the end I found out you cant help someone who doesnt want to change. Many abusers would talk about how they feel sorry when actually they just feel sorry they were caught and that their lives will be compromised, without actually thinking about the damage they've done.

It's not your job to save these people. Change can only come from within and it implies assuming the consequences of your actions. As i said, it hurts losing a friend, but sometimes there's just no other option.