Hello there, welcome aboard.
I read your explanation and the attached file, and will try to say and explain my point of view. Apologies for the massive wall of text.
Massive caveat of I-have-no-medical-expertise and my own treatment etc is all in Japanese being in Japan as I am, and so my system experiences in Britain and technical term experience in English is very limited.
So arm yourself with a caravan of salt deliveries before reading.
Hoarseness and smelling smoke seems to suggest a respiratory tract infection. Lacking key nutrition like indeed vitamin d makes you more vulnerable to infections among other things. Lacking folate can also causes tingling and numbness in the hands and such. Degenerative spinal disease can be caused by, other than just age, indeed infections. Overall, your explanation seems to mostly lead in the direction of [missing nutrition lead to infection which lead to other issues, and it was then treated with indeed the necessary nutrition for such issues.], after which you then had more MRIs just to make s.
The written note about that says that, well, since you still had symptoms they wanted to see if there was perhaps a reason like indeed MS behind it. And well there was no such thing it seems. What little white spots you have appear to be within normal, you have no syrinx, and your central canal is just big which is apparently not related to well neurological issues but which can also push further onto where you then already had issues in the spine due to the built up liquid. The contrast agent did not reveal active lesions or anything like that.
So err overall it seems you have no such disease like MS and your symptoms appear to basically be from the initial nutrition and degenerative spinal disease issue. Googling around a bit, it seems that basically won’t heal by itself. The proper nutrition and then stuff like massages and other physiotherapy, or just plain inflammation reducing steroids, is about all that’ll help, apparently.
It’s a bit like when you brush your teeth too forcefully after acidic food. Over time, the teeth get worn down losing their enamel and your gums pull pack revealing more of the teeth. This basically leads to pain, and it is a you lost something that cannot really be regrown kind of issue, meaning the treatment focuses on reducing the pain and the issues it’ll cause for you.
Degenerative spinal disease, it seems, is sort of similar in that you lose the soft cushions in the spine and leave the bones rubbing against each other sort of. You cannot regrow the cushion by yourself, so it’s various therapies and painkillers to reduce the impact on you like indeed the symptoms you mention.
Well, if they think so they might not think they need those extra checkups anymore as you indeed suspect.
While you do have similar issues to those with MS, the reason seems to be very different and much more physical/less immune system related.
That is again just my highly uninformed and hastily googled etc. tentative opinion. Now is the time to call in those camels carrying sacks of salt, apply liberally before you believe any of my nonsense.