Re: Advice on Running
You could also have him do some barefoot running. Running barefoot or in VFFs tends to be self-correcting on your form because most people will run POSEish if they don't have shoes with thick cushioned heels. Doing it on grass or sand is a good way to start if you want to minimize impact.
Start things out short like you said--50-100m repeats at 90% of max speed or something like that, and don't do too many at first.