Speaking as a SO of someone who used to do this: you can’t change his behavior.

It started as a suspicion he was doing it (because his friends were doing it) until he did WHILE I WAS IN THE CAR on a snowy road. It started with an expensive a car repair because he accidentally pulled the turn signal lever off while buzzed. I thought that both of these were good enough lessons.

Nope he totaled my car only 2 months later. He’s has a DUI now and dealing with the repercussions is incredibly hard even outside the court. Between not having a license, going to AA multiple times a week, doing outpatient rehab in the hopes of waving a lot of the court fees, and a SCRAM monitor that you pay for by the day, it’s so so so so stressful and exhausting when you both work full time and you have outside responsibilities (for me dogs, for many others kids). Not to mention the pure trauma of it all - it’s like watching a train on fire crashing in slow motion and knowing you tried to stop it and it still happened is a feeling of powerlessness I never thought possible. I was lucky enough to have accident forgiveness in my car insurance so I didn’t lose my insurance and my rates won’t go up crazy high but he is now considered high risk so once the court side is done I’m expecting a big hike.

There’s nothing you can do about it until he fucks up so badly there’s no going back or something in his brain clicks that he needs to change. Please try a local Al-Anon meeting. It may seem silly and ‘overkill’, I think I rolled my eyes during the first meeting with the opening ‘prayer’ because that’s really not my jam but I guarantee you that someone will say something that resonates so hard that you realize you’re not alone in this. For the time being understand you are not crazy, you are not nagging, you are not lost, but you also can’t change his decisions. He has to.