Your body can make about 50,000
IU worth in 15 mins of unprotected sun exposure. Craig takes 5,000
IU daily and his level is still within the normal old limits. So yes, I think vit D cannot hurt, along with some calcium.
The magnesium can help with muscle spasms in a normal healthy person. In MS I believe they may help a little, but spasms are caused by the brain sending wrong messages to the nerves and muscles, so the mag helps a little bit but not as much as in a healthy person.