Re: Is he or isn't he?
On the functionality question -
my husband, who's now recovering, has always been very successful in most areas of his life, even when he was drinking at his heaviest. He wears a suit every day, is a vice president in his organization, is an adjunct professor at a university, does triathlons, and coaches little league baseball. He never drank before dinner, and I almost never saw him drunk that I could tell. He also had a very high tolerance for alcohol, so he could drink for hours and not seem affected, which is a red flag.
I'm not sure there is ever a definitive answer about whether someone is an alcoholic. It's a progressive disease -- it's not like one day you cross the line. If alcohol is affecting your life and your relationship, then there's something here for you.
I hope you find what you're looking for.