If it makes you feel better, you could report what you know to the police, so they can keep an eye on him.
I maintain (and I know something about it), that all of your information would be considered too "stale" to launch an investigation, much less to prosecute or obtain any search warrants.
He may, indeed, be a pedophile. The police can't lock people up for being perverts, only for committing crimes. The fact that he lusts after underage girls isn't a crime. There is no "thought police". The police can only go after someone who has committed a crime (for which they have actual evidence) or for someone engaged in ongoing criminal activity (for which they have a basis to investigate).
If it makes you feel better to tell the police what you know, do it, and then let them do their job. That may be thanking you and putting the information in a file somewhere. And then let it go.