I would advise him to try to get a routine with rules. No screen time 1 hour before bed including TV. Low to no lighting.
Then maybe he can learn some relaxing breathing exercises or meditation to do before bed.
Even though his mind is racing at night it is important to be in a dark and quiet environment although I use some sound to help me sleep.
I listen to thunderstorm or rain noises at night.
Maybe even talk to his doctor about melatonin supplements. 
Having a routine where you do the same thing every night helps your brain know when bedtime is. Avoiding blue light increases melatonin production and he might be allowed to take a small dose of melatonin a few times a week to help him adapt to this schedule if his doctor says it's OK.