Must say that I'm a cous-cous fan when it comes to packing food, just add it to a mug of hot water (no need to simmer) add a flavouring (cup-a-soup for the lazy) and you've something to fill a big hole and packs easily, more so than noodles, rice or pasta. Polenta or semolina is just as easy.
Also oats ban be eaten either dry or with hot or cold water added. (Honey or even diluting squash can be added to sweeten it up if you like and again easy to pack.) Can also be made into bars and oatcakes if needed.
Powdered potatoes don't agree with my stomach so I avoid them but can be a useful bulker/thickener to stews and soups.
I like to hit the ethnic food section in the shops and usually end up with some form of jerky, salami, smoked meat fish. Also when we were heading off on expedition we used to raid the Chinese supermarket as they have a plethora of dried fish, meat, vegetables, fungi (and things that I don't know quite how to categorise!) and were always helpful in telling you what you could do with what. Was also a cheaper way to get our scran and make it more interesting.
As to how long I could survive out of a shoe box of food, well survive yes, but as Crocodile Dundee says "It taste's like S***!" But you can eat quite well if you put some imagination, research and spice into stuff.
On the butter front I either use good olive/rapeseed oil or put some butter in those
Coghlan's Squeeze tubes, better than taking a whole tub of butter, peanut butter, whatever and they don't leak. As fat is something you will crave after a while.
How you intend to prepare the food is a consideration to what you take. I like pulses and beans, but on a fuel poor expedition they could be problematic due to prep time. But they're very packable and nutritious. We got round it by using any spare hot water from other tasks (clean) to prehydrate them in daily batches in wide mouth Nalgene bottles. (You can also use them as mini-greenhouses to make sprouted grains which are very good for you.)
Popcorn is another light thing to carry (un-popped) and it fills you up no end, plus it's fun to make/eat whilst watching the in-camp movie (the fire) and kids tend to like it too. It's seemingly one of mans earliest snack foods; evidence dating back some three and a half thousand years for it.