EdwardHutchinson

You may find it worth searching for the Dr COIMBRA High Dose Vitamin D3 protocol for controlling the symptoms/progression of MS and other autoimmune conditions. Coimbra is using amounts in the region of 2000iu per kg daily together with high dose magnesium and dietary calcium elimination. There are support groups on Facebook with case histories so you can see the progress and effects of these treatments (which have to be monitored by Coimbra protocol trained doctors.) However as an initial stage maintaining 25(OH)D in the 60 - 80ng/ml range (normally measured in indigenous peoples living outdoor minimally clothed lifestyles) is safe and may show if higher dosing would lead to further improvement.

Role of Magnesium in Vitamin D Activation and Function
https://jaoa.org/article.aspx?articleid=2673882
You may find ensuring magnesium status in the brain aids vitamin d activation.
Timeline (Bioavailability) of Magnesium Compounds in Hours:
Which Magnesium Compound Works Best?
http://sci-hub.tw/10.1007/s12011-018-1351-9#

In order to keep the basic cholecalciferol form free and bioavailable in serum where it's half-life is just 24 hours we need daily vitamin d3 dosing sufficient to maintain 25(OH)D level at/above 50ng/ml 125nmol/l
Dietary Vitamin D and Its Metabolites Non-Genomically Stabilize the Endothelium
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0140370
We only see optimal inhibitition of inflammation at levels around 50ng/ml
Vitamin D Inhibits Monocyte/macrophage Pro-inflammatory Cytokine Production by Targeting Mitogen-Activated Protein Kinase Phosphatase
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3368346/