That sucks! I wish I could help but I’ve been unemployed all year. It sounds like you’ve verified what you know about him. In that case, I would do two things. One, check with the police and see if he’s even allowed to work in such a position. Frequently pedophiles are required to stay a certain distance from children, and having a key to your place would not qualify! Secondly, tell everybody else in the building so that they will take precautions and put additional pressure on the landlord.
I believe in giving people second chances, but this doesn’t sound ideal. Perhaps he could get a maintenance position where there are just adults and / or work evenings.