I personally would not stop the meds until you have the sleeping under control. Changing too many things at once can make it hard to figure out what’s going on. Also, if you stop the meds before you do sleep training, then you’ll always wonder if he’s crying because of the reflux or pain. On the same note, you’ve described sleep behaviours that sound like nocturnal acid breakthrough. I know that no one wants their child on meds, but really these meds are quite harmless, so better safe than sorry. That’s just my opinion.