I never got the impression that he was an alcoholic, though.
It’s so interesting that we can all play the same game and come away with different impressions! I agree that we don’t have enough info to be sure of a specific diagnosis of alcoholism, but for me the facts that Wyll seems to drink too much, seems drunk when spoken to at camp and displays behaviours that I’ve found typical of people with not entirely healthy relationships with alcohol were the things that seemed most obvious about him. But of course everyone is free to interpret the story and characters in whatever way makes most sense to them!