Don't take any calories off your BMR.
I had calculated your BMR earlier I thought, and it was close to 1800 kcals, based on the information you have given.
You have to multiply your BMR by the activity level as well, I usually go for moderate in my off season (1.55) and then intense when I am getting ready for a comp as I do so much cardio.
Gatorade is full of sugar, I am not fond of sports drinks at all.
The only place that a simple sugar really works well is post training, when you want an insulin spike to transport glucose and amino acids into your muscles.
If your calories have been that low for some time, I wouldn't all of a sudden start eating 1800-2000 kcals a day.
I would add about 10-20% of what you have been eating, so add 130-260 kcals the first week or two, see how it goes, then add the same amount the following week, and so on, until your calories are in a more healthy range.
That is the good news hun, you can EAT MORE and still build muscle and burn fat.