I don't think cheerios is a sensible way to get high doses of niacin. It is fortified in some milks, most breads and grains. But i had to take 500 a day to get improvement on mood and lips. I was doing 200 previously for 3 months and nothing, well they were a tiny bit better, but not significently. If you can get quality pills do that. Usually 100 mg a pill.
As for food, you guys need to understand that this may not be the issue for YOU. It's what contributed to poor health for me, and i think it relates to EC. My suggestion is just to see what you can and can't eat. you may be fine. And there's no reason to cut out all the things I can't stomach for yourself, because that's not your stomach. Basically, everyone is different. Eating these certain foods doesn't trigger EC, it's the long term effects of poor nutritional absorption in the digestive tracts, aggravted by food intolerances and compounding stress.
So, you really need to ge yourselves tested as a starting point. Wheat and dairy are just common ones that's all.
As for what I can eat, just about any real food. Every kind of vegetable and fruit. Nuts and seeds. None-gulten containing grains- ex- Rice (and they make rice bread, rice pasta, rice cookies, rice everything, though it's not on par with bread all the time), gluten free oats, quinoa (great protein source), meats, possibly goat or sheep milk products, I haven't tried them yet really. I drink rice milk. Corn- cornflakes are great for breakfast. Lots of things...eating out can be hard, but some places have gluten free menus, and I've found most servers are aware of gluten intolerances.