Hi Spod,
If you don't want your calories then don't have them. It is completely down to you. Just make sure you are getting your 2 shakes plus a 600 cal meal as this is what is providing you with your nutrition. You may find that in a couple of weeks you will start to want them as some people do start getting hungry on the plan once their bodies have adjusted to it. If you find you are hungry make sure you add your snacks.
With regards to how much do you need to exercise that is very difficult to say as it will be different with different people. Anything is better than nothing, even if its just climbing the stairs or going for a walk. It all makes a difference.
1lb is apparently equal to 3500 calories. If the recommended daily allowance to maintain weight is 2000cal and you are having 1000, then in effect you have 7000 calories less per week making a 2lb loss. That is the maths but it doesn't necessarily work in practice. Don't forget that muscle does weigh more than fat so too much exercise may show as a gain if you are building muscle mass. Many of us take measurements; waist. hips, thighs etc because even if the scales don't move, this doesn't mean you aren't shrinking.
Hope that helps
BL x