Marketpress authorize and capture, gateway discount, order addons

1.In marketpress is it possible to have the authorize.net gateway authorize the funds and then attempt capture later after admin reviews and confirms the order?

2. Between the time the order is authorized and the time it is captured is it possible for admin to add to the order? We would like to be able to add on fees for additional driving time, ect.

3. After an order is complete are we able to add to the order and bill additional items to that customer? Is there a way to place orders from the admin side?

4. Is it possible to offer a discount for using a specific gateway? I would like give a discount for cc payments.