There is a possibility that he is abusing alcohol, though 2-3 drinks is almost OK, if he keeps it there and if it is not part of a pattern. However, given the rest of the stuff you are talking about, you may have an angry, budding alcoholic on your hands. Most cannot and require total abstinence. If he comes from an alcoholic family, his odds shoot up. On the other hand, he could also be behaving like a grouch because he has a primary depression.
Depressed people drink to blot out pain.
Unfortunately, this is a vicious cycle since alcohol increases depression. Drinking to mitigate depression may in time lead to alcoholism. In this case, treating the depression may clear up a lot of stuff. Often, depression, alcoholism, and anger coexist. He probably needs treatment in all 3 areas.