In my opinion he VETTED him, too much on the line for DQ and the franchise for him not have. It's clear this has been in works and not something thrown together. As to his contract, I don't know and neither do you but NFL franchises are not generally know for be foolish.
Hey, it's just my opinion too. Not a problem if we differ.
I'd say the USC AD had more on the line than Quinn does. He also likely relied on Pete Carroll's rubber stamp.
Contract-wise, I don't think there's a way to wordsmith any kind of alcohol-related clause in a way that won't leave the franchise open to litigation if the guy gets fired.
Also, several NFL franchises have been shown to be foolish or at least negligent in handling of a myriad of issues the past few years. I don't look at any of them and feel confident they won't do so in the future.