I'm glad your son is OK, OP. You and your DH did a great job - exactly what my mother did for me. If anything, she was too kind by letting sympathy beyond the critical period become the normal order of things, but I have always been the type to fear her disappointment more than anything else. If your son's anything like that, I'd worry more about him at uni than at home, because in non life-threatening circumstances you'd have no way of knowing what a state he was in, and this is possibly, against all logic, a relief to him. I am now at uni (got my worst years out of the way before attempting it), teetotal, in what I would describe as a raging drink culture, and what I see around me isn't pretty - not that I blame people for having more or less the same experiences I had at eighteen. (For the record, I only stopped drinking because alcohol eventually became so incompatible with my mental health that I couldn't even have a couple without triggering suicidal crying fits.)
I would, for the benefit of the thread, like to give the example of my much younger friend. His parents are the type to take the piss in the morning and make him tidy up his own mess, but would have searched the town for him at any hour sooner than let him die of hypothermia. They also, such is my understanding, drank around him when he was a child, had him mix their drinks for them, and particularly his father will on occasion get paralytic. They didn't pick their battles, so now he won't listen to their advice because of the time they (smokers) well-meaningly forbade him to smoke, which did nothing to stop him and has made him view them as hypocrites. What might have been reasonably firm tactics mean nothing to my friend because the example his parents have set seems to him utterly inconsistent with their suggestion that he partake in moderation.
His brother didn't drink for the longest time, and thinks of heavy drinkers as idiots, but will occasionally have a couple. Friend has been injured drunk before, can be a bit verbal and at one point went through a phase of insisting on lying down "just" for a bit in freezing parks at night. (We looked after him of course, and I'm sure that students would be the same, but I know that Friend was the "baby" of the group starting at 15, that not everyone will put up with repeat offences from the same individual, and that alcohol makes me unusually tolerant.) We have a few mutual friends who are/were just as into it as Friend, but they are far more aware of their surroundings. I don't like to brand people as "survivor" or "not", but in the case of alcohol some people cannot stop once they have started (I am guilty of this) and do not have the sense of self preservation or social capital to ensure their own safety.
I really hope that the above does not come across as patronising. In response to posts about how much (if any) discipline the morning after, reactions to parents' own alcoholism, and teens "babysitting" each other, I just wanted to offer a "horse's mouth" account of my own fairly recent experiences and the frank justifications my friend gives me as a peer rather than a parent.