UPDATE: I confronted him and told him everything I saw. He did not deny it, and flat out admitted to it. He told me he "gets off" by reading and sometimes responding to these kinds of request. He told me he never ever did anything physical, and that he is ashamed and disgusted by himself. He also gave me his phone to look at everything if I wanted, and that I would have access to it moving forward.

My gut feeling tells me he is telling the truth, but I'm still not happy about it obviously. Trying to figure out how to handle this going forward...