Baby's father who drinks and smokes weed

He's saying he wants to be back with me, that he wants us to get our own place and be a family for when baby arrives. He drinks & smokes weed. I don't know how often he drinks, maybe almost every weekend. But I do know he smokes weed every day with his friends because he told me. He never smokes or drinks when he's around me. Although he's turned up to my flat a few times high which I've told him not to do anymore. Obviously there's nothing I can do, I can't make him stop. All i can do is tell him to make sure he's never drunk or high around the baby. I have spoken to him alot about it. He said there's nothing wrong with smoking and drinking sometimes when he's out with his friends. He swears he would never do it around the baby and that if we live together, he would never do it at home. Just upsets me because I wish he was like he used to be, he never used to do it but what can I do 😔 apart from the drinking and smoking there's nothing I can complain about. Even though we haven't been together he's been at every scan. He's been so excited ever since he found out he's having a son. I just have no idea if I should get back with him or not.. Does everyone else agree that there's nothing wrong with what he's doing?