If I understand you correctly your still having heartburn despite PPIs and H2 blockers. That's where I was the last 3 yrs. I was even doing OTC antacids and Carafate liquid.
A pH study is pointless because you're already having pain despite meds. You're refluxing.
Has an endoscopy shown if your lower esophageal sphincter stays open? An esophogram/barium swallow would show how badly you're refluxing and how large a hiatal hernia you may or may not have.
Also, a motility study would determine how well your esophagus is working. This particular study is crucial for the determination of eligibility for the LINX procedure.
As long as you have Barrett's no acid should touch your esophagus. It's an even higher cancer risk.

Just make sure you mega dose on B12 ie methyl cobalamine. After 2-3yrs of PPI use liver stores of B12 are depleted and that can cause a host of other issues down the road. PPI use raises the pH of the stomach so protein bound B12 from food can't bind to intrinsic factor and get absorded in the gut. The gut will passively absord 1% of nonprotein bound B12 which is supplements are a good option.
Just ask the right questions and the Drs will figure it out. It's imperative you self advocate though. Never be the passive patient.