I'm absolutely positive that starting a strenuous exercise routine about 20 years ago is what has kept my body so strong and mobile - after probably 36 years with MS - and many other medical conditions, too .
I'm not even positive which symptom is from which and after all, I'm pretty old, too, so the fact that I can still pick up my cane and scamper up several flights of stairs (did I really describe myself as a scamperer?) with all the leg issues I have is pretty good evidence.
Over the years I've kept adding exercises until I've got one for just about every part of my body, although my PT found a weakness behind my knees; I added stretchy rubber band strips to address that. Another PT suggested my walking would improve if I walk on my toes, and the vascular doc said it would improve my veins. So I awkwardly tiptoe from room to room. Kegel exercises reduce bowel/bladder problems.
I'm positive that I'm secondary progressive, but my leg muscles and hand grip are so strong they don't register as a deficit in an exam. I use a finger exercise ball that has practically eliminated a finger tremor, allowing me to continue to type and play piano. I've always thought that I figured out how to get rid of L'hermitte's many years ago - thru exercise - but don't know for sure. It's 99% gone, though. My walking speed and 'peg board' speed continue to improve at my yearly neuro visits, even though I can feel the MS sloooowly progressing.
Besides those things, I credit regular morning exercise for reducing my fatigue and raising my energy level for the day. And my mood. I think you can find studies that suggest that's the case. I exercise first, then often head out for a 10-11 hour day of work and class. I walk toe to heel backwards for my balance.
I wouldn't even give up my exercise and stair climbing when they had to tape my kneecap into place for 6 weeks - completely unrelated to MS. It's been 6 years since then and I still haven't needed surgery on it. And, most important, I continue to exercise my brain and my sense of humor.
Even if exercise wouldn't improve or eliminate the specific MS symptoms you want it to, it will improve your health and your attitude, and it just plain makes you feel good. That should be enough. I'm glad you're already working toward diet and exercise goals and hope you achieve them. Please keep us posted on your progress!
P.S. I don't do every exercise every day, of course, but do try to rotate all of them into my life regularly, along with many others. I've got a lot of body parts that need fixing.