Sounds like you are doing the right things. The fact that he had no PCS symptoms before the recent fall is a good thing. The fact he was physically active before the fall is a big plus. Lots of quiet rest is very important. Go easy on the workouts, and have him stop immediately to rest if he gets dizzy or starts getting a headache or blurred vision. Good nutrition, B complex vitamins and good hydration are also important. All brain injuries are different and they heal on their own schedule. As head injuries go his is very recent and significant improvement should be expected.