Hi @michaelsz, I also take vitamin D3 as part of my neuropathy supplements but not at the high doses that you have taken. I take 50 mcg daily which I think equates to 2,000 iu. I've not read of neuropathy symptoms from vitamin D toxicity. Here are a few references that might help explain it better.

-- What is vitamin D toxicity? Should I be worried about taking supplements?
https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/vitamin-d-toxicity/faq-20058108
-- Vitamin D Toxicity: https://www.ncbi.nlm.nih.gov/books/NBK557876/

I also have balance issues with my neuropathy and do exercises but also focus on other things to hopefully help to prevent falling. It's good to hear that your symptoms have improved since you stopped taking vitamin D. I usually discuss the supplements I take with my primary care doc at my annual checkup. Have you discussed the symptoms and improvements with your doctor?