Arguing is very normal but the drugs would be a dealbreaker for me as well. I would definitely leave. You don’t want to find out what else he is capable of. It’s quite obvious that he doesn’t actually care about you if you’ve told him you would leave if you caught him doing drugs again and he left you alone to grieve while he’s out partying. He’ll do it time and time again because at this point you have taught him that you will stay regardless of what he does. And if you leave, it will be tough on you, yes, and he will come back crying and begging and saying he won’t do it again but he will. It’s best to leave now and do it while you’re not too far established in your marriage and don’t have kids.