Since you are already taking the important ones...I have another suggestion.

It might be a good idea to switch to all activated B's.
That would be
methylcobalamin for the B12
Pyridoxal 5 phosphate for the B6 pyridoxine
methylfolate or folinic acid for the folic acid.

Some people do not convert well or at all. Methylation polymorphisms is a big subject now, and given your educational level, you can appreciate this subject.
Methylfolate is just coming back OTC from Solgar. It was removed by Merck to make more $$ for them by putting into RX meds. I am not sure it is available yet. There is a thread on Vitamin forum about it. But Folinic acid is OTC and not expensive. Source Naturals makes it. It is OTC Leucovorin which is used to supplement chemo patients.
So using all 3 activated forms of B12, folic acid and B6 might be more efficient for you. There is an RX version of this mixture called Metanx if you prefer and can get your doctor to write for it.

I already gave you some other suggestions in PM.

I don't understand your reference to possible OD? Is that short of overdose? One does not have to OD on amphetamine to have negative things happen. Just long term use can exhaust dopaminergic systems.