No. You don't.
You have evidence that he may have been drinking underage. But that doesn't make him an unfit parent. And really - your ex is not yet 21 apparently...so how old is your son that he has such a sad face? How old are BOTH of you?
What you should be focusing on is the reason/s you want to relocate. THAT is often the most important thing. So...why do you want to move?

