I also have numbness in my face, lip ect. @ years with the same symptomes you have mentioned. for meanwhile - all the test are OK and my neurologist said it is - probably - idiopatic small fibers sensory neuropathy.
The skin biopsy is recomended in such a case, but I didn't do it yet.
Good luck with the tests. (ask them to check sjorgen - too, just in case, also very common with NP)
all the best