My wife and I want our son to fix it, but I'm losing confidence that he will.

He's a sophomore. He was the starting RB on the sophomore team last year as a freshman and had an extremely productive season before getting hurt (in practice). He had 3 games of over 140 yards. The varsity coaches saw most of the games and like him a lot.

When football officially started in June, my son started practices with the sophomore team again.
In July, the varsity coaches pulled him from sophomore practice one day and told him to go to varsity.
After two-a-days ended, the sophomore team and varsity teams practiced at difference times and he was told by sophomore team coaches to practice with them too. So for the past couple of weeks and for the rest of the season, this is his practice schedule.
3:15PM - Varsity practice starts
6:00PM - Varsity practice ends
6:00PM - Sophomore practice starts
8:30PM - Sophmore practice ends

He's the only kid in the program with that schedule. He probably won't play much on varsity so it may be in his best interest to drop from the varsity team. He gets so beaten up in varsity practice, that he doesn't have much left when he gets to sophomore practice.