hi i have 14 month old with servere reflux and other GI issues i know how frustrating it is, i dont know much about the threrapy that you are refering to but though i would relpy i noticed that you said they are considering outting him back on a PPI but seen as it s the vomiting that is the isue not the burning it may not help much if any, i was wondering if they have ever done a gastric emptying study on him or tries him on a motility drug such as dompereradone thjat helpd the tummy emty and can sometime reduce the puking episodes, you may have already tied it i dont know but thought i would let you know just incase its somrthing to talk to the dr about

good luck hope something works