Did this behavior just suddenly get worse? Does he have friends or drink alone? Have you talked to him at all about it rationally when he wasn't drinking?

Two to four beers a night is not horrible for a man, can just be a nasty habit. What's his work like? No clue what in his life is causing him to decide drinking/being drunk is a good idea and why it is "progressing".

Do you have friends/family and a support network you can talk to? Does he? I'd talk to him and then his friends/family or work buddies, etc. and see what is going on. I don't understand how he can "leave" and you have no clue. If this happens on weekends, I'd have my brother or another male relative/friend come over and then follow him or go with him, etc. if he wouldn't tell me where he was going or even follow him myself. It doesn't sound like there's any communication happening?

He could be ill or have another major life problem he hasn't discussed with you and is trying to drown it. I'd marshal the family's resources, friends, therapists, etc. to see what help there was for "sorting" it out. If I couldn't figure out how to sort it, I'd look into a legal separation. I wouldn't live with such behavior without some answers as to what's going on and "why" and some idea of whether or not he was interested in changing the situation.