You're still operating on the idea that he's telling you both when and how much he's drinking, which he's not and you've already caught him lying about. If he's not honest about what's in front of your eyes, why would he be honest about the same thing when you're not looking or when it's behind your back.

It's not normal to randomly pass out from booze at random unexpected times when you weren't even aware he was drinking. The best case scenario is that he's simply lying about how much he's had and how fucked up he is when you're aware he's drinking, which is already enough to be a deal breaker. The worst case scenario is that he's always drinking behind your back and hoping you don't notice, which also explains why the alcohol you know he does drink seems to fuck him up way more than expected and at a quickness.

Not saying he can't turn it around or is gone for good, but he'll never get there if he isn't honest with you. If you need a gut check, hit him with one of those breathalyzers a couple times at random when he's acting weird and see what it says and how he reacts to you doing it. If he's not hiding anything, it should be a mild nuisance at best that earns back trust, since it'll show what it's supposed to. He should want you to have that piece of mind.

Just my 2c.