It takes 4 weeks for bone to form around the fracture. Once that happens you can start to rehab the muscles. My big worry is if he is in a boot for 6 weeks then he will have severe atrophy of his calf's and ankle muscles. That will take 2-4 month before he can be back to full strength. The longer he keeps it in-mobile the longer his return is.

from someone who broke his shoulder last year ...just keeping it in a sling for 3 weeks has causes havoc for over a year.