Your symptoms are obviously severely affecting your lifestyle
Although I cannot offer a complete evaluation, I will make some comments based on the information here
Have you had an evaluation for obstructive sleep apnea? - this can cause mouth breathing (dry mouth in the morning), feeling of being unrefreshed in the am, with daytime sleepiness, frequent nighttime awakenings. This can be evalauted with a polysomnogram (sleep study) , which involves staying overnight at a sleep facility and having your breathing, movements, sleep and brainwave activity measured.
Diabetes can cause a range of peripheral nerve problems, which can even occur in the face of 'normal' glucose levels
it can be difficult to diagnose, but a center that does skin biopsy looking at epidermal nerve fibers can do this.
Of course, structural disase ie a mass or growth causing the pain and discomfort should be evaluated with radiological imaging.
The Cleveland Clinic is among center that can do both the sleep study and the 'neuro'-skin biopsy on a routine basis.
It is unlikely that the vagus nerve is involved as long as a strucutural lesion is ruled out
Good luck