I'm mad at my so for drinking
Does he drink a lot?
He does, but that's not actually why I'm mad. I'm mad because he also drives when he's drunk.
Being upset that he drinks too much is fine but your second concern is far more important. he's driving drunk and is eventually going to get himself or someone else killed. You need to do whatever it takes to get him to stop, even if it means calling the police on him.
I'll confront him and make him stop. He's not stupid, he'll probably get it.
Good, it sounds like you're doing the right thing here.