1) You're given a range so you'll have the flexibility! There's not a single number that causes weight loss. The range they give you is literally so you'll know the least and the most you can eat, and still lose weight. Your body isn't a calculator, and there isn't a single magic number.
2) You can eat anywhere in your range for weight loss. Some days, you may want to eat more, some days, less. Anywhere should provide enough of a deficit for you to lose weight. Some people like to eat at the high end on workout days, and the low end on sedentary days. It's up to you; experiment to see what works. At no time should you eat *below* the minimum number. You need at least that much to get the nutrients your body needs to function.
3) Really, no. What matters is not what you eat day to day, but your calorie deficit over the period of a week. you won't lose weight faster by eating consistently at the lower end of your range. This isn't all or nothing :) I regularly eat at the top of my range most days, and I'm still losing steadily.
For more information on the hows and whys of the calculations here, check out the Calorie 101 article: www.sparkpeople.com/resource/calorie_calcu