It seems like you have LPR (silent reflux) IMO. Regular antacids don't usually do anything for this, I would ween yourself off the PPI, if they are doing nothing (you have to lower the dose slowly over a month or so, be patient).
I honestly don't have a solution for you though, as I am going through the same thing (constant mucus running down the back of my throat, runny nose for the past 11 months). I do have a little heartburn though, so I take a small amount of antacids to manage that, and they actually seem to make my mucus worse with the more antacids I take, as I stopped them for 3 weeks and my nose/sinuses cleared up.
Post Edited (jarhead) : 12/7/2017 9:22:08 AM (GMT-7)