OP, that must be really worrying for you to watch. My uncle died of liver cirrhosis due to alcohol and I have a cousin who's currently terminally ill with a nightmare combination of cirrhosis and cancer.
A few years back I was heading down a dark path myself, drinking a bottle of wine a night and thinking I was 'ok' if I didn't drink one day a week. Denial is a very powerful force. I'm not even sure why I was drinking so much...boredom? Enjoyed the feeling? Always made me feel nicely relaxed before going to bed (even though I'd wake up in the wee hours with a headache and the sweats).
I can 100% see how it happens though. 1 bottle becomes 1.5 bottles and so on and as it increases you tell yourself you deserve it, that you work hard, that you can stop when you want to.
And then all of a sudden, with no warning, everything just goes a bit splat. For me I ended up in A&E with a dangerously high heart rate and BP, not helped by the nearly two bottles of red wine I'd just drunk. I think I could just suddenly see how my uncle and cousin had gotten to where they were and I did not want that horrendous life for myself.
Anyway, I don't think I was at alcoholic stage but I was well on my way. But the fear of God had been put into me and that gave me the push to get started. I got a drink tracking app and just started slowly tapering off.
I do still drink now but within my weekly units and I don't feel like it's got this hold over me in the same way. I think your DH needs a proper heart-to-heart or some kind of intervention as it sounds as though he thinks he'll just feel a bit rough and will then stop, but in truth he could end up having a life-changing medical issue which gives no warning. If he were to have an accident while driving and was found to be over the limit, he could lose his livelihood too. Not to worry you further but he's living a very risky life.
I'd really recommend a drinking tracking app (Drink Aware do one) and committing to religiously tracking every glass. He will probably be horrified when he sees just how much he's consuming. That little 'red - this is likely to be seriously damaging your health' indicator on the app was a massive help to me and many, many times stopped me from having 'one more small one'.
I hope you're able to have a honest chat with him.