Welcome to the board, John, Melanie and Drew.  My son is 2 1/2 and is a salt-waster as well.  That first year was rough.  My son had wet burps (wasn't a projectile vomit) till about the time he started on solid food.  His labs aways came out acceptable, so we just fumbled through that first year.  Looking back, I have my doubts that we did all the right things.  We are not with that Endo anymore.  My son was on the liquid Cortef (which has been discontinued), florinef and 1 ml. of sodium solution in each bottle.  It was a battle getting him to finish the bottles containing the salt, so I made 4 oz. bottles and he drank the one with the salt first.  Other parents have given the salt solution just like the cortef in the bottle nipple before a feeding.  Thank goodness about 1 year of age we stopped the sodium in the bottles because he was getting enough salt from table food.

It wouldn't hurt to discuss this with your Ped. Endo.  There is an injectable hydrocortisone for infants under 1 year of age that might be a solution if indeed your son is not getting the meds to replace what his body doesn't produce, due to the spitting up.  Is he due for labs soon?  I hope you find some answers to put your mind at ease regarding this situation.  Just remember, it does get easier and you do develop a routine after a while.