I used to be at 11% BF, I gained a bit of fat back due to a bulk I was in, however, that 13% is probably wrong due to the weight not changing from water intake.
At any rate, I told people they can just eat exactly what their RMR (I prefer BMR) is and that in itself is a deficit since it doesn't account for everything else you do (like daily movement to and from work, etc.). Just remember, as your weight goes down, so does your RMR, so you need to go lower as your weight does (or else you are just closing the gap to maintaining weight).
Also, find out how close that RMR number is to your body weight X 12 cals/lb. That should probably give you a number within 100 cals of each other. If I were to take a guess that 1500 sounds REALLY low. My wife, who is 5'3" and 130 lbs, she gets close to 1400 for her RMR. I am not so sure I think your number is right. How many calories do you eat a day again?
I used to use a heart rate monitor religiously, I have since backed off from it but I might start again if I don't show any measurement/scale changes in two weeks. I have a Polar F55 (Polar F55 Ice Aluminum Heart Rate Monitor with Wearlink Coded Chest Transmitter with FREE shipping included! Also known as: polar f55, f-55, f 55 heart rate monitor) except that might be excessive for you. I would suggest something like this for your purposes Polar F4 Heart Rate Monitors with FREE shipping included! I like that one because it tells you when you get into your recommended zones and keeps tracks of calories. There are even cheaper ones that don't have as many features. But for the extra 20 bucks, the F4 is worth it. Also this place is VERY reliable...
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