Did anything come of your concern that they might want to put him on expensive proprietary supplements... or is that down the road a ways still?
I just saw something about apple cider vinegar...
here. May or may not be anything useful there. Pretty potent stuff though. My dad used it to (over) treat a toe nail fungus... figured if a little was a good a lot was better... his nail fell off.
Oh, and have you tried gram/chick pea flour yet? Supposed to be very high in protein but gluten free...
Stay strong.