For my non-breakfast hotel rooms, I enjoy bringing English muffins, bagels, and/or bread, with peanut butter (jar or packages) and jelly (in packages, so no refrigeration is needed). You could also pack a toaster if you need these sort of things toasted to enjoy and the hotels don't have them. The peanut butter and jelly can be used for sandwiches for the hike. I also enjoy the portability of apples, bananas, peaches, etc. for this type of trip.
For snacks, your favorite granola, cookies, chips, or crackers packed into small snack sized zipper bags are handy, or if you feel like splurging, the 100 calorie pack section of stores have sweet and savory options.
Unless you're going to a fancy place, steakhouse, or Hawaii, a decent meal can typically be had for $10/person, and can many times be split (stick to water as a drink).
I'm a solo traveler, but for myself, I typically budget $30/day unless I'll be in Hawaii or a Disney park for some reason ($5 for breakfast, $10 for lunch, and $15 for dinner).
Your gas estimate seems reasonable. I always like round numbers in my estimates.