Functional is a stage, not a type, of alcoholic as far as I'm concerned.
He may be in a "functional" stage for awhile longer, but in the end, like Lexie says, it always begins to unravel.
I was the same as Lexie--high status job, respectable, no problems with DUI or other typical issues. But gradually becoming less "on top" of things and I finally had the sense to see this and stop.
You did the right thing.