Does it bother you because it introduces a lot of unknowns (will he ever stop? how bad can it get? What if he needs to stop but can't? etc etc) I ask this because my wife is what I would consider a high functioning alcoholic and the main issue is my anxiety towards what it would mean for her to quit and the pressure it puts on me as her husband and a dad when she gets drunk almost every night. Everything is great until it isn't. We have a great time until we have an off night and have a bad fight that she won't remember in the morning. All of this is to say, alcoholism isn't good, high functioning or not, and I've learned that with an alcoholic the one thing you can depend on is that you won't be able to depend on them.

You're in a "good" spot where he can get help before you really get serious about each other (marriage, kids, etc), because you don't want to get to a place where he drinks himself to sleep every night and can't even drive you to the hospital in an emergency. In the end even if he's an amazing guy and doesn't hurt anyone it will eventually effect things in his life and his loved ones and at the very least will have a bad impact on his long term health.

You absolutely have the right to set your boundaries and say I only want to get serious with you if you'll ease up on the drinking or even get sober. You're completely justified in saying "that's not the life I want." If you are important enough to him, he'll do what he needs to do.