Hi and thank you for updating the community, though not many are posting they are still checking in from time to time :D
I honestly don't know very much about Vit D 12 deficiencies, nor how they can mimic MS as well as a few other medical conditions but i came across this awareness site awhile back https://b12awareness.org/vitamin-b12-cobalamin-anemia/ and if it's of any benefit to your self or others in similar circumstances it's worth passing on.
It's amazing that something like a Vitamine B 12 definiciency can cause so much damage, though i don't know if i'd be confident it was the right answer if the MS specialising neuro didn't also mention B12 def as a potential explanation too.
Quix probably hasn't posted now for about 6 years or more...
How you doing overall now though?