170lb, 5'1 female eating 1000cal a day doing 45min fast pace walk on treadmill 5days a wk. rate of weight loss?

Depends: Your rate of weight loss depends on many factors. If its just calories in versus calories out, then you would lose weight fairly rapidly with this program. But you are eating too little. You should try for 2 pounds per week of steady gentle weight loss and not damage your health. I would think you need a diet of at least 1500 calories per day.

It depends: On the type of diet (how much protein and carb) but you should at least be losing 2 lb. Per week if not more on such a restrictive diet. Try to get 40% of calories from carb, 30% protein, 30% fat and stick to more whole foods rather than processed starch and sugar. Also add some yoga for core strength and vary your speed on the treadmill between fast and slow.

1-2 lbs per week: Based on your information, you burn about 1450 calories a day at rest and an additional 220 additional calories per workout. By eating 1,000 calories a day you should lose an average of 1 lb a week if you lead a sedentary lifestyle and up to 2 lbs a week if your lifestyle is very active.