In your position, I would keep it casual in my head.
Is he a heavy drinker? Does he have a drink problem? Who knows. At this stage, it doesn't matter particularly except that, due to your experiences, it matters a lot to you.
Break it down a bit.
Most people will smell of alcohol if they have had a heavy drinking session the night before. So let's take that.
What is your line? Is a heavy drinking session occasionally ok to you? If it is then, then a one off like that isn't a massive issue. However, if that's not ok with you, then it is.
It's hard when you like someone except for 'just this one thing' but this one thing is something that is hugely important to you. And these 'just this one thing' things usually are. Perfect except for his drinking; perfect except for his porn use; perfect except for the sex...
From my perspective, an occasional night out or weekend with friends that left someone smelling of alcohol wouldn't bother me - an occasional blowout is fine. But if it were often - every night out or every weekend or they'd been drinking at home alone, I would know that there wasn't any chance of it becoming a serious thing. If I were up for something casual then fair enough. If not, i would end it.
It is true though, you will ruin it anyway if you don't trust him. I start from a position of trust but, if it's broken, I won't hang around however good everything else is.