yeah, that seems too low an intake to me.
one trick used by old school bodybuilders was to reduce intake to various levels so the average
would be what you want but on somedays you may have it 400 higher or 400 lower or even around 4500 (maybe once a week as a treat). This helps to keep your metabolism from dropping, because the body goes into a kind of survival mode and adapts.
I think a pound is worth about 4 to 5000 calories, so you could lose a lot of weight by significantly reducing it by as much as you say. I would keep your average a little higher though, no more than half. on any day if you want to keep muscle.
In terms of BMI, i am 200lb and nearly obese on the bmi scale. 29 points. It makes no sense and is totally outdated because i am healthy and slim looking. What really matters in your body fat % you can measure this through various ways, electrical impedance, water etc..
You should also weight train as it will allow you to hold onto more muscle, burn more fat and keep up your metabolism. hope this helps