how long is the flight? do you really need to bring that much food? i'd make a frittata-muffin thingie with veggies in it and eat that --far more satisfying that nuts or a plain egg. i don't snack at home, so wouldn't be bringing "munchies" on the plane either. generally when flying, for me it's a hydration issue more so than hunger, since the cabin air is so dry.
as for cooking at the hotel, i guess i'd wait to see what's in the local market, rather than planning anything now. if you're not traveling to a foreign country, am guessing you can make pretty much whatever you would at home.
for eating out, avoid chains and keep it simple. grilled meats or fish, steamed veggies with real butter. salads, ask for o/v on the side. tell your server you can't have gluten or sugar. am assuming you won't order anything deep-fried, so the oils become less of an issue.
As I ate the oysters with their strong taste of the sea and their faint metallic taste that the cold white wine washed away, leaving only the sea taste and the succulent texture, and as I drank their cold liquid from each shell and washed it down with the crisp taste of the wine, I lost the empty feeling and began to be happy and to make plans.
– Ernest Hemingway