Good luck with your endoscopy! I hope you get some answers to why you're suffering so many symptoms. Keep in mind that sometimes these test don't notice the more subtle symptoms that can cause certain sensitive individuals some real difficulties.
I was one of those low GERD symptom testers, but had some serious lung issues due to my mild/average reflux (according to the tests).
I went ahead with surgery, and my lungs responded beautifully. I'm so glad I trusted the opinions of my family and asthma doctors, regardless of what the GI doc found.
We're all here to support you through your search for answers!