Hi Albeit
Your case is somewhat complicated by the fact that you have symptoms that are not well localized in space and time.
You don't say how you got the diagnosis of SFN. There is a definitive test for this condition, a skin biopsy of the foot and another for the thigh for control purposes. You also should have had a nerve conduction study. SFN is not generally a diagnosis of exclusion, as you implied in the last sentence of your first paragraph.
I don't think this forum is the place for you to be told what tests to tell your doctor to order.
I share your frustration with the lack of time allotted for medical visits. The neurologist will not be able to explain all your symptoms with one diagnosis, or generally with one visit. His/her job is to get a good history and exam, then get the appropriate tests in the correct order (the results of one test often lead to another test).
One thing that might help is for you to list your symptoms, diagnoses, and previous test results in chronological order on a piece of paper that you can show to him/her. Then try to relax as much as possible, and let the system proceed.
Good luck, and keep us posted.