Were any of the chiros specialists in Upper Cervical chiro like NUCCA or Atlas Orthogonal ? Did they do something different than the 'twist the head and pop the neck' treatments ?

Have you had any gentle traction with gentle manipulation (like a massage) of C-1 and C-2 ?

I have been treated by many chiros with a drastic difference between those who could help me and those who did not.

I have not heard of people struggling to take B vitamins. Some say B-12 leaves them feeling awake. I wonder if something else was happening when you felt buzzed and agitated. I suggest you give it a try again. Maybe you are so deficient that even a starting dose makes a difference. Start with a B-50 complex and add 250 mcgs of B-12. The rest of the regimen should not have any issues. I was started on it cold turkey 30 years ago and it was life changing.