Hi ecb1171
Welcome to NeuroTalk
.
It sounds to me that the neurologists you have seen have done a good job of ruling out various possibilities.
The general information in this link may help you.
Small fiber neuropathy: Symptoms, treatment, and causes
There is a lot of information on the Web, not all of which is reliable. One reliable source is PubMed (there is a link to it in the "Quick Links" menu on all NeuroTalk pages.) PubMed contains about 30 million citations of the biomedical literature.
When I searched PubMed for "small fiber neuropathy inosine" I got no results. This suggests that there is no reported evidence that inosine is of any benefit in treating small fiber neuropathy.
Best wishes.