Is he really drinking as infrequently as you're claiming/think? Might be useful to diarise when and roughly how much. And bear in mind he's likely drinking more than you think anyway. Being able to drink a litre of whisky and still be fairly with it is worrying! That indicates he has a pretty high tolerance.
And the drink driving is COMPLETELY out of order!!
To me yes he seems to be an alcoholic, and he IS abusive, verbal abuse and the emotional abuse of putting you in a position where you daren't challenge him IS abuse.
I know it's considered a faux pas on mn but honestly you knew what he was like, why did you have children with him? Or at best you knew becoming a father didn't make him grow up and take responsibility after having your first so why have a second with him?
I'm the child of an alcoholic too, it's bloody miserable and far from an acceptable way to parent but you don't sound ready to accept that:
A he's an alcoholic
B you're enabling him to a degree
C that there's nothing you can do about it
D that the best thing you could do for you and your kids is leave!
He has no reason to change as things are now, he can just carry on, ignore your "nagging" and still get the benefits of a family life and home.
Only you can change what you will tolerate.
Greggers I think it's you that doesn't understand what an alcoholic is, binge drinking is definitely recognised as one form, frankly your defensiveness and minimising on this thread strongly suggests you have issues of your own with alcohol.
"It’s his only chance to drink.. " except it's not is it? You've already said he's drinking a fair bit at home too. And that's the drinking you know about! I'm afraid the drink driving incident is unforgivable of BOTH of you, you knew he'd had a drink, enough to be belligerent and you not only let him drive (you could have called the police or at least enlisted a friend or family member to intervene) you got in the car! You certainly could have refused to get in the car, I would have and have done so on a few occasions AND told the potential drivers if they get behind the wheel I'll be straight onto the police and meant it!
"I'm a substance misuse worker" bullshit! And if you are you need better training! Or else you've become so jaded and immune you need to quit.
"I understand the importance of having an identity as well as just a Mum" which doesn't have to involve alcohol.
Not all alcoholics drink every day or even every week.
In this case he is drinking most days/weeks anyway, and that was clear from op's posts even before what YOU claim as a drip feed (and if you were a substance abuse specialist you'd be experienced at reading between the lines anyway) he's not only drinking when he's out seeing friends, op is doing a LOT of minimising. Someone who can drink AT LEAST a litre of whisky and still seem remotely capable of driving definitely has a problem!
"Didn’t realise I needed to write a detailed report" you didn't - it was obviously clear to myself and others prior to that supposed "drip feed" post that your husband does have a major issue with alcohol.
Op contact a support organisation for those close to alcoholics eg al anon and honestly again I say as the child of an alcoholic the best thing you can do for your kids is leave. He's not interested in even discussing it so you've little chance of getting him to change his behaviour any time soon, your eldest will start noticing and being directly affected and you cannot underestimate the harm this can do.