I'm thinking of encouraging my depressed son to go to college 1500 miles from home
Why do you think that distance is going to help him?
I was going to build a path for my son.
I think you want what is best for him, but sending him so far away may not be. It comes off as ignoring him and sending him out of site out of mind.
He needed the push.
I think that you should get him some help first before you give him that push. I think that it is bad to just ignore the fact that he is having some mental health issues.