Hi Jmak,
I'll answer your questions in the order you wrote them.
Distilled water is best, R.O. water is great, water filtered through ceramic and charcoal is next best, followed by whatever clean, filtered water is available to you.
A rough guide as to how much water to drink daily would be 1 quart (litre) for every 50 pounds (22kgs) of body weight. Surprisingly, if you keep that up along with the MMS protocols it will be the best way to overcome Duuytrens Disease. If you find it going straight through you at first, don't worry, your body will adapt over about a 3 week period and you'll stop having to run to the bathroom too often.
Vitamin C in most natural foods is not a problem, and if you have oranges and/or grapefruit and a cup of tea 4 hours before you start your MMS protocols for the day that will be fine. With the grapefruit, scrape some of the pith as well, it's a great blood vessel detoxifier and will assist your condition. Avoid processed foods.
Coffee can be consumed a couple of hours before or after the protocols.
It is definitely the DMSO that results in that smell so you could go without it during your conventions, but keep up the MMS regardless.
One more thing would be to exercise your hands and fingers often - make a fist and squeeze then relax, then open the fingers outward and stretch. Also press the opposing finger tips from each hand together & push against them so your fingers come together down to the knuckles while keeping the palms apart.
Good luck with it.