I don't know what other tests would be helpful but maybe some one else can help you there. I do know that 2 Nexium a day made me terribly sick and nauseas. I switched to Prilosec and that did not make me sick.
I don't have any advice to offer you other than read the posts going back a ways. There is lots of information here and I've learned a lot just from reading them. Good luck.

I've had an upper GI, a motility (gastric emptying), an MRI and a CT scan. All normal. This week is my EGD with biopsy. We saved that for last because I've had bariatric surgery and it's rather touchy to do that testing on me. I had to find a gastro who'd worked with VSG patients before.
As for what other tests, I would say perhaps food sensitivity. I can tell you that since I have cut out gluten and sugar I do feel better and when I am "bad" I know it within 20 min and for the rest of the day. A donut hole is all it takes and instant burning and pain. I know it's because certain foods cause more inflammation but you know it's hard to always be good, isn't it?
I'm doing a lot of reading on alkalinity/acidic stomach issues. I noted that oddly I feel better when I eat something you would think would hurt, like salsa than I do when I eat something like pudding, which you would think would soothe. Seems all the ppi and h2 meds we take may be some overkill and we need some acid in there or our stomachs gets too alkaline and neither alk or acid is good if out of balance. Anyway just some thoughts.

Thanks Tanners. It's awful when you take a medication to help you feel better and you end up feeling worse. Good that you found one that is better for you.

Nina, thanks for sharing. What is the motility test? And what would an MRI show? (Those are the 2 that I didn't have, but they were never suggested). Am sorry that en endoscopy is risky for you. Good luck with it. I've heard others say that gluten is an issue. Have you ever been tested for celiac disease? I don't think I have an issue as for a bland diet, I'll often have just toast or a bagel. Yeah, touch about the acid...I guess the theory is that our stomachs are irritated/inflamed so the acid that is required to digest our food, harms us since we have no protective lining.

For the motility test (to check for gastroparesis), you show up early with an empty stomach and they give you two scrambled eggs with radiation in them, then you lay down flat and stay still for 90 min while they see how long it takes for it to go through your system. It was the hardest test so far, it hurt to lay there with just eggs (which bother me anyway) in there. The mri was something he did to try to avoid the EGD, but no luck, he needs to go look.
No, I don't have celiac as it turns out, just sensitivity, but jeez do I have sensitivity! Doc said it might have been positive if I'd been eating it more recently but I'm not willing to do that just for a test. I know I can't eat the stuff. I still think what we eat is 1/2 the battle... but I also know how really hard it is to be "good".