There is literally no evidence that any of this happened. That was a rumor going around based on some Reddit post of someone claiming that they were a child actor who were abused on the sitcom they acted on. People thought it was Erik because the post claimed that the father on their show went on to be a bigger name on another show, but a lot of the other details mentioned in the post conflict with what is actually known about Erik's life.
Fucking thank you, I keep seeing that fucking Reddit post [which could just as easily be a creative writing exercise on OP's behalf] bandied about as definitive proof that Dewey/Erik Per Sullivan was molested while he worked on the show and I should think by now, given how many other child actors were involved in MITM, if someone on the show were a child rapist/pederast, we would have had someone either come forward or there would have been an arrest of some sort. By and large if someone is a pedophile and has progressed to molesting actual children, they don't just 'stop' one day, and eventually wind up arrested. We would know by now, where there's fire, there is most usually smoke. It sort of reminds me of all of that shit with Nickelodeon where people [especially on Reddit] act like Dan Schneider is some avowed, proven child rapist when in reality the accusations were "he was weird about putting foot stuff in his shows" and "he did some kinda weird shit from time to time that made people uncomfortable", the former of which... well, I don't know, maybe some of it is odd in hindsight but he did create children's shows, kids tend to find feet funny. And if we're going off of "did shit that made people feel uncomfortable sometimes" and treating it as evidence of pedophilia, by God that's going to be an extremely long list indeed.
I'm just as apt on cleansing Hollywood of the child rapist cabal of Baal worshipers or whatever the fuck as anyone else, but some of this shit grows legs and just ends up being schizoid shit. I suppose the theory is that Erik got out of acting and "disappeared" due to having been molested, but in reality he could have just as easily fucking decided acting wasn't for him and he didn't like public life or being well-known, sometimes people do that. Likewise Redditoids get pretty weird about him, trying to find recent photos of him or wondering where he lives now and shit, leave the fucking guy alone, he clearly isn't interested in having a public image anymore and wants to do other things and how much of interest [that is new] is he really going to have to say about a show that ended 20 years ago when almost all of the other people involved in it have given interviews and have always been willing to discuss it?
People on the subreddit just have a weird fucking obsession with the guy and likewise a lot of people have an obsession with believing that every single child actor/musician/etc. was brutally raped for years all throughout their career, I don't claim to know why, but it's clearly not the case for everyone who got involved in entertainment at a young age.