i haven't read any of your previous posts so i don't know what else you've tried besides zantac, but my 2nd baby (4.5 mos. now) had reflux and i eliminated dairy in my diet and it stopped. it is obvious b/c any time i eat a little bit he is spewing all over the place again. maybe you've already looked into that but just thought i'd mention it.
it might be better to try diet changes first before doing all the stressful scary tests. We have had to do that, too, with our older ds and I'm with you, it was awful and we didn't learn anything new. In my experience, most regular peds and gi doctors aren't very open to the diet sensitivity idea.
I hope you find a solution!