I certainly agree with your last statement about Minoxidl and Nizoral. Since this is quite a unique case, maybe also consider the haircomb. It's received mixed reviews but I know of people who swear by it, so it might just be worth looking into...
-Hair transplant wise- He needs to be careful, he's really very young and until the hair loss stabilises he is at risk of getting a transplant and ending up with a very odd hair pattern, or losing it once again due to donor instability. I personally don't think he should even consider it right now, other treatments can halt/regrow his hair, at least until he's a bit older and more able to assess a greater range of options.