I have a couple thoughts. First would be to measure instead of focusing on the scale, like desertmountain said. Although a pound of muscle does not weigh more than a pound of fat (a pound is a pound), the muscle is more dense and takes up less space, so if you are gaining muscle, measurements will show faster than the scale. The "body" tab has a place to enter them.
Second, I put your values into this calculator: Calorie Calculator - Daily Caloric Needs
Some folks feel it works for them, some don't. But even on the "extreme fat loss" calculation, it gives you 1700-some calories. Maybe your system is slowing because of the drastic reduction? Maybe try keeping it closer to the 1700 side and also read the info about calorie cycle zig zag, which keeps your body from adjusting itself to the predictable; that may help if you try it. Possibly varying your exercise may help also.
Congrats on your perseverance! You will get there.