I am not going to do justice to your long post in this short reply, but I would say that the Neurontin is primarily found useful for the typical burning and electrical zaps of PN. If you don't have those symptoms, I don't know that it will help you even if you do have PN.
You can have quite severe leg pain as a symptom of advanced neuropathy, mine is hereditary, but the typical symptoms usually accompany or precede that. Your case does sound complicated. Did they do an EMG/NCS?