To answer your question about Vitamin D - there's been much research possibly linking low Vitamin D levels to the development of MS. Many people on this forum (me included) have had their Vitamin D levels tested, and they were found to be low. Now there are some studies looking at the therapeutic value of high doses of Vitamin D. It's generally believed that supplementing with Vitamin D may help prevent MS (a lot of good that does now, I know). Less clear is whether it helps those who already have MS. However, there isn't much to lose by taking some vitamin D everyday; it's inexpensive, and won't cause harm unless it builds up to toxic levels. How much to take is a tough call - the best way to figure this out is to be tested, and see where you fall. It was recommended to me that MS patients take 1000 IU's/day, along with 800 mg. of calcium. Many (me included) are taking levels much higher than this (4x to 6x).
As to the research studies, I don't know too much about the ones for progressive MS. You might want to check out the Drug Pipeline forum here:
However, I would think that the primary consideration would be what Wash. U. has going on.