Parenting advice ?

So I have a 3 year old son and I try to keep him away from his dad but every blue moon he sees him at church. Reason why when I left him 2 years ago he had started doing drugs and was abusive to me, stole my car in the middle of night and money out my purse, he stole money from his own mother, he even busted my lip because I asked him to get the baby a bottle. He went to jail for a few weeks for pawning stolen things. I finally left after so much .. Hes been calling claiming he doesn't do any drugs but does smoke weed but won't do it around him ! I told him no and I'm wondering am I doing him wrong because my son wants to be around his dad ?