I agree that it can almost be distracting to get too focused on labels, but at the same time I sympathise with your urge to find a benchmark or yardstick - I was with my husband for six years before I was able to fully recognize and face up to what his drinking meant to me and to our relationship, and one of the reasons it took me so long, even though the drinking had been there from the beginning, was my own confusion over what "officially" counted as "too much" or "dangerous" or "alcoholic."
At one point, I normalized the behaviour and my own shock about how much he was drinking by telling myself that he was very tall and perhaps therefore needed more alcohol and/or could handle more alcohol than most people. Or I would think, “Well, he’s had a hard day.” Like you, I was also confused because there were times when he would be sweet and caring and funny and at those times, I would start to think my concern was misplaced; he was also never "roaring drunk" or loudly abusive - just often tipsy, sometimes inexplicably cruel (only to forget the next day the devastating things he said), and often unreliable. But you learn to live with all that, somehow.
For me, there were three things that made the difference to my own measure of what felt OK and what didn't: first, he started drinking in the morning, and when I asked a couple of therapists about this I was told it was a very unhealthy behaviour (in retrospect I’ve thought I a lot about this - imagine what it must do to your stomach to wake it up with hard liquor. Someone who is willing to do that, repeatedly, is actively harming themselves). Second, it became clear that he was relying on the alcohol to get him through any kind of difficulty or even strong emotion, and it became impossible for me not to see this as a dependency rather than a conscious choice. That was when I also started noticing that he never, ever, left a glass or can of alcohol unfinished.
And third, his reaction to my concerns about the drinking when I finally voiced them out loud (denying that it was a problem, responding that "you have flaws too", refusing to seek help of any kind, finally lying outright) showed that his priority was the drinking itself: my distress, my fears, the breakdown in our relationship, the increasingly obvious negative effects on his health - none of these was more important than his being able to continue drinking. That’s when I moved out and started going to Al Anon.
I understand how living with someone, especially someone you love, who drinks, can dull your instincts; and for some reason, many of us feel a profound need to be "fair" and not "dramatize" or “give up”- but somewhere inside yourself it sounds as if you have a recurring gut feeling that "this is not OK." Trust your gut.