Sorry youre going through such a rough time
I guess just continue to let him have 10 or 20mls throughout the day and at least he'll be getting in his liquids.
Someone once told me to put a few drops of vanilla essence into the formula to get baby to drink it, and it definitely worked for me!
Could definitely be other ailments upsetting him also, but I presume if you've seen a paed he has ruled out these things.
Sounds like you're on the right track by going to see specialists.
Some babies with severe reflux problems require feeding tubes just to make sure they are getting food. Hopefully it doesnt get that way, but if he really does have health issues it may be the only way for now.
Poor baby. And poor mommy