i think you could still be a chef depending on your signs symptoms and progression to date, and also whether you are open to some of the diet and lifestyle changes that help so many with ms. alternately what about doing something along the lines of dietitian/nutritionist, or food journalism? what if you did the chef thing for a little while, making sure to take care of yourself as much as possible, just to pay the bills, while looking for a more sedate option?
by contrast i find that my active and often heat stressed job keeps me in good shape and it's days with nothing but sitting that really mess up my functionality.
I had to do an internship for school, six months, and during this six months I had two relapses which is what led to my diagnoses in the first place. So that being said I don't think that the kitchen is the best place for me...you know the old saying ''if you can't stand the heat get out of the kitchen'' there is a reason that is so well known. The kitchen is definitely one of the most stressful hottest places that I have ever been.
I have a job, don't get me wrong, and I make decent money, but not what I would be making if I were a soux chef or an exec chef in a 5 star restaurant.