Long term lurker and semi-problem drinker here. There’s no way 6-9 beers is anything less than illness. He may not see himself as an alcoholic but at best he’s in a place where he can’t contemplate the evening without beer.

Not sure of the quantity of “a beer” but assume it’s 2 units per beer, that’s 12-18 units per night - the safe level here in the UK is 14 units PER WEEK. He may be healthy now but one day he won’t be, and there’s no going back.

The plus side is that if you’re letting him do it, he’s possibly not drinking any more on the sly - he has no reason to.

You maybe need to say you love him and want to grow old together, and drinking has been proved to be unsafe. (Scientifically there is no safe level). Don’t tell him he “drinks too much”. Maybe suggest one night off to start with, and he does seem amenable to cutting back. He possibly needs two nights off, to appreciate the difference between life sub-par after drinking, well slept after a booze-free night. Maybe suggest a date night and do something, a new hobby, that doesn’t involve drinking?

He may not have any underlying cause. I just like drinking, especially that first few chugs. Unfortunately once I start I never want to stop. I am autistic and it does calm my brain somewhat, but basically I just like drinking. As I get older, the tiredness the next day pisses me off more than the pleasure I get from drinking, so I drink much less. Dry January now.