Look into something called Postural Tachycardia Syndrome, or POTS. I don't know much about it, but it sounds similar to what you're describing.
Has your son ever had any neck problems/injuries? Headaches?
My 15yr has that, doctor told us it is Orthostatic Hypotension. He supposed to out grow it, that was 2yrs ago, he still gets it when getting up from the recliner or lying position.
Good thing it does not affect his sports. It does have to do with the blood flow to his brain.
I don't have it that bad, but in periods get almost blackouts when standing up quickly (vision fades) slight dizziness and also when looking up. The usual useless MD have no explanation, except that Im tall, thin and blood pressure on the lower end (still in normal range). I personally think it has to do with blood flow. I've never heard of loose "stones" in the ear...sounds odd. I also have post nasal drip, doubt they are related :D