When I went through rehab for the last time the reason I succeeded then when other efforts had been miserable failures was that the people who were helping me stressed that getting clean meant not only breaking free from drugs, but also breaking contact with the scene and the people who had facilitated, enabled, and tolerated my addiction. I have been 33 years clean now, but I still get up and walk out if hard drugs appear.
I know the parallel isn't a match, but I think the same thing applies in the case of you and your boyfriend. This other guy who is boasting of his liaisons "every now and then" with a 9 yo boy is a criminal and should be reported to the police immediately; certainly he's no friend. IMHO you and your bf need to stay well clear of characters like this. They can only do you harm.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)