My perspective is if you have to ask whether or not he is an alcoholic, there is your answer.
If he were not, the idea of posting here wouldn't have entered your mind. Your concerns are valid as are your feelings. Until he decides he has an issue and wants help, I'd see it as huge red flag in terms of the issues that will crop up in marriage.
When I feel confused about the behavior of my ABF and how it affects me, I pretend that a friend of mine is in my situation: What advice would I give her?
I will be honest though and tell you that it is a long road for him to get to where he acknowledges he has a problem and an even longer road to recovery.