"Functioning alcoholic" is a term that we argue about here, upon occasion.
We generally believe it is either a stage of alcoholism, or the mask that an alcoholic can show to the rest of the world until the disease progresses too far to hide it any more.
My XABF (ex-alcoholic boyfriend) would drink in the morning, although he was rarely drunk until the afternoon, when he'd have about a pint of whiskey in a timespan of about 20 minutes. But that's just him - everyone is different.
I will say that among alcoholics, no drinking pattern is "unusual" - it's all whatever they can justify to themselves.
I know it's sad, but it is your father's decision, not yours, not your son's... And your father is still in the grips of the bottle, so the alcohol is doing all his deciding. It has nothing to do with him valuing alcohol more than valuing a relationship with you; it has everything to do with the power of the disease.