I hear you - this can all be so frustrating! I'm on Prilosec for maybe very short segment Barretts, first endoscopy was inconclusive, second was negative, but GI doc is still suspicious of Barretts on second endoscopy. I have osteoporosis in my spine, and Prilosec is bad for that.
I forgot to mention, my ENT recommended Reflux Gourmet, which is similar to Gaviscon Advance, using sodium alginate to create a "reflux raft" above stomach contents. I didn't care for Reflux Gourmet, but find that Esophageal Guardian by Life Extension, with alginic acid very helpful at bedtime.
Good luck - I truly hope that you find some relief! It's so difficult coming up with a strategy that works and I too am still trying to manage my reflux so I can go off Prilosec.