Finding medical advice online is always hit or miss, but I had severe upper back pain for quite a few years that matched many of these characteristics. To my astonishment, the problem turned out to be gastric and related to stomach acid. After lots of tests that ruled out lots of things, it was eventually solved by an doctor who had a similar issue himself, and suggested that I try a high dose of Prilosec just to see if helped. I was extremely doubtful (since the pain was not in my stomach) but since like you I was desperate, I tried it. Behold, it helped almost immediately, and within a couple days I was almost pain free.

I eventually figured out diet and sleep position changes that let me stop taking the Prilosec (mostly sleeping with a wedge and allowing several hours after eating before sleeping) and now I mostly have the problem under control. At the least, knowing the cause and how to fix it makes the occasional pain a lot more manageable. While this might not be your exact problem, consider that it might be. And if nothing else, have hope that maybe you'll eventually find an equally unlikely solution that gets you past this current pain.