I was going to comment that I wouldn't go below that mark. But I also noticed that you've already lost 155 pounds! Good for you! You seem to have a good idea of what you need to do.
But, for what it is worth.... I do track both food and exercise calories. While I typically don't eat back all exercise calories, I'm using myfitnesspal and it is designed to put you at the correct calories to lose X amount of pounds per week. I just don't want to eat so far under the suggested calories that I don't have energy to make it through workouts and throughout the day. It won't help me at my job if I'm thinking about how hungry I am or how weak I feel. I want to lose weight, but I don't want to lose too much muscle mass. I want to come out on the other side feeling strong and fit.
But, as I said, you've done amazingly well!