BMI is meant to help people who don't exercise get an idea of where they are and where they should be. Athletes can be close to 0% body fat and still post as obese on a BMI scale (which is BS).
Your handheld body fat indicator should come in useful, but don't take the "lean body mass" figure to indicate how much muscle mass you have. That figure contains bone mineral mass, water mass, and other things as well. Take the fat percent measure and when it goes below 20%, you can be considered healthy. That may come when you weight 180lbs, 185, 200, or whatever. The total weight does not matter really because muscle mass plays a huge role in the total weight. So just use fat percentage as a measurement and you should be fine. And, as others have said, once you get there, you'll know.