Remember to revise your goal in a way that takes into account what you (we) have done to our original architecture! IOW, a formerly 400-600 pound person who gets to a "normal" BMI will probably be emaciated and deathly ill...because she will have a couple of stones (at least) of excess skin hanging on. Additionally, you have built bone mass by making your skeleton carry all that weight. In response to that demand, you have bigger, stronger, heavier bones than someone of similar height with no hx of morbid obesity.
So "normal" for you will not be as low a number as " normal" for your identical twin sister who was never obese.
Thrilled that you're doing so well.
I had a goal of 145 lbs. I actually got as low as 155, and looked horrible. Looks aside, I was terribly weak and fatigued. I am happily resting at 170. Tossing away my hopes on a scale number, I have pinned my success to my lab numbers. I'm much happier with sound lab values.