I don’t think a guy in his 50s hooking up with a guy in his 20s is inherently abusive or evil-it is indeed a large subculture, as you’ve discovered-but I think you should stay away from your son’s friends for hopefully obvious reasons. You have a lot of anxiety about your interest in younger guys, with good reason, beyond your suspicions that this could all lead to child abuse. “Porn addiction” isn’t an actual American Psychiatric Association DSM diagnosis-a problematic relationship with porn that takes on features of addiction (keeping you from obligations, for example) is grouped in the realm of hypersexual disorders, which is to say that not using porn doesn’t necessarily mean you are “cured” of an underlying issue. If that is not your situation, I’d talk to my therapist about the porn addiction you say you had and kicked.
