Glad to hear that Oliver is home. I'm sure it is boring and frustrating for a 21 year to feel totally wiped out and have mom and dad monitoring his every move. My only advice to him would be to take it slow and steady now or pay the price later with a longer recovery. I had an experience similar to his gas station encounter. I walked to a Burger King about a week after my surgery in LA. All of the traffic, sights, and sounds completely overwhelmed me and I was beat for the rest of the day.
Those first few weeks are not a lot of fun. The best thing he can do is walk outside on uneven terrain. This should help him with his balance and to start building up his endurance. Hopefully, being outside will help his state of mind as well.
Hope things progress for him, but it does take effort and patience. A good dose of humor doesn't hurt either.
Ken