McDonald’s lattes? I wouldn’t trust anything that comes from McDonalds. You can check out the ingredients in their foods at nutrition.mcdonalds.com. I looked up the sugar free vanilla latte and the ingredients are whole milk, espresso and sugar free vanilla syrup. The question is in what the syrup contains. A lot of those have fillers/thickeners like modified corn starch, dextrose, etc.
Chocolate doesn’t automatically have gluten. It depends on where the chocolate comes from and again if it has corn starches/dextrose or high fructose corn syrup, etc in it. There are several sources of true grain free chocolate online.
Are your sensitivities perhaps delayed allergies that can be eliminated under the right conditions? I have 13 delayed allergies, including sugar cane, and I’m doing 6 months without the allergenic foods/environmental allergies, while sticking to a grain free diet. The idea is to heal so that my allergies will go away since the lymphocytes that react have a six month life span.
All the best to you!