Hi Mel -
It's possible you have a true allergic reaction to something, not just an intolerance, or it could be a severe sensitivity, as that happens too.
Bactrim bothers lots of people especially if it's given in a high dose. It may be the sulfite in the drug, but it gives people without the sensitivity stomach problems too. I can take it in smaller doses.
Plain, fresh potatoes do not have sulfite. Frozen potatoes, at least in the USA, always have sulfite to keep them white. So do canned and dried potatoes. I can't figure out if there could be any sulfite getting to you from your husband's breath, although it could indeed knock you over from the smell. Canned fruit could have sulfite to keep the color, or it could be in sugars added, especially corn syrup or dextrose. I always have a problem with a whole serving of tomato sauces, but a taste is OK unless you have an anaphalactic reaction - true allergy.
Keep on writing down your foods, also drinks and medicines. Use a small notebook with dates, times, reactions especially immediate and an hour or two. Migraine sufferers can react a day after eating sulfites.
Look up the link I posted for an entire book on sulfites. It has how to calculate how much sulfite you are eating in your meals.
It will take a couple of months to get a good list of your food intolerances. After a meal in which you react you should break down the ingredients and - CAREFULLY - preferably with the direction of an allergist - eat a small portion of one ingredient at a time. Look up on the search box at the top of the page "Challenge Testing."
I can eat the meat in a hamburger, also the lettuce and tomato, but not the ketchup, onion, pickle, or mustard. Some bread gives me a reaction also, unless it is home-made. Commercial bread often contains "dough conditioners" which contain sulfite.
When you get your list together, check it against all food intolerances and allergies. You could have more than one! Sulfite is not the only allergen. MSG, saccharin, many other things can be a separate problem.