I am happy to answer your questions 
1. No, for vendor fulfilled orders you would need to have an order completed by Mpix after approving it.
2. This is currently not possible unless you are self-fulfilling orders.
3. No, once an order is placed it will need to be approved by you. If it is not approved after a month has passed the system automatically cancels the order and refunds the customer.
4. There is currently no way to offer multiple print discounts for vendor fulfilled products.
5. You will need to create these options with custom products.
It really seems like self fulfilling your orders will give you the options you are looking for.
I hope that this was helpful! 