target calorie deficit

Hi there,
I am 172 cm (5' 6) and weigh 77kg (170lb)
Healthy BMI for my height is 55 to 74 kilograms. (121lb - 163lb)
I'm nearly there !!

I'm 'aiming' for 55kg and but will just stop when I get to a weight I'm happy with.
I know that you are supposed to set your calorie deficit based on how much you have to lose, and that 77kg to 55kg is still a lot to lose.
So I am wondering if I should still be aiming for 1000 calorie deficit per day or if I should reduce it since I am quite close to 'healthy' bmi. I have been on 1000 cal deficit for 5 months or so and have lost consistently without feeling hungry or lacking in energy. I want to get the weight off asap, but to do it healthily, of course.
Thanks