I’m so confused re: daily calorie requirements

If your goal is to figure out how much weight you will lose per day if you don't bring enough food than 3500 Calories / lb is the number you need to use. Generally this is the more useful number for most people's calculations. When determining the energy supplied by your food than the 9 Calories / gram is correct.

Beyond that more information on the composition of human body fat while interesting is not all that useful in meal planning.

Curtis,
Don't sweat it for 5 days. Over about forty years I usually figure
1.1 pounds per day of high density food
1.5 pounds per day of medium density foods.
2.0 pounds per day of regular food.

I have spent up to 6 weeks out with 1.1 pounds of food and only lost 7 pounds. Conversly, I have spent 14 days out and lost ten pounds with 2.0 pounds per day.
I always seem to loose some weight when I am out.

A LOT will depend on you, what you do, your metabolism, as well as the type of food you bring. At BS camp we were eating MRE's for two meals and cocoa, oatmeal, and coffee for breakfast. This was OVER 2.5 pounds of food, but I still lost some weight. Turns out I was only getting ~3400C if I ate everything.

When you gain or lose weight you are adding or subtracting lipid content from adipocytes. Mostly you are not changing the number of cells; just their bulk. It makes sense to ignore cellular components other than lipids in the context of fat gain and loss.