Why can't I stop after one glass of wine?
The limit gets set by a woman who has had nothing to drink, then handed to one who has. That is the whole problem, and it is not a character flaw.
Am I an alcoholic if I drink wine every night?
You are asking a search engine because you do not want to ask a person. Here is the answer nobody gives you.
What is grey-area drinking?
You function fine, nobody is worried about you, and there is no crisis to point at. You also think about alcohol far more than you would ever say out loud.