A human eating only 1000 Kcal per day would only be able to support a body weight of about 60lbs if sedentary. Are you sure your estimates are accurate?
The website fitday.com is also designed to compute calorie and nutrient intakes from food, and might be a good way to double-check your spreadsheet calculations.
Oh, that's why I mentioned the cookies. I do eat a lot of those (and other sweets). The ~1000 calories is only for the "real" food that I consume, but it is, to the best of my knowledge, an accurate number.
Recently I decided to try an intermittent fasting diet. To do so, I had to figure out how much I could eat on my off/down days. I realized I didn't have a very good idea about how much calories my meals have, and as I was thinking about it, I started to get curious about my diet overall. How many calories do I get a day? How much of it is from fat? Do I get enough vitamins? Etc, etc, etc. All very basic questions, and since my meals are very regular, there was an easy way to find out!
(Note: anytime you feel curious and are about to find something out, make some predictions. I didn't, but I really wish I did, because I was very surprised by my findings.)
It took only a couple of hours, and here is the result.
If you scroll down, you can see that my usual Breakfast+Lunch+Dinner only nets about 1000 calories and gives 30% daily value of fat. No wonder I crave cookies and chocolate so much!
There are many surprising results that I got from this. And knowing that I've been eating like this for the past few years... Wow. This is the epitome of a low hanging fruit. I can't believe I didn't do this analysis earlier!
Edit: I was not trying to say that I only get 1000 calories a day. Of course I get more than that, but the rest is from cookies and post-meal sweets. I always thought I just have a sweet tooth, but the fact that I wasn't getting enough calories from my main meals can also explain this.