1) You have to list plans, but they don't verify so you can change them.
2) You have enough time in Shanghai, but given how much time in Beijing I'd add another day to Xi'an. there's more than the warriors (I think there's a thread titled that).
3) You have ample time in Beijing. You can certainly use those days to your advantage, but with that much time you *might* consider adding another city, or spending 3 full days in Xi'an, allowing for the city one day, warriors one day, and another excursion from the city on a third day.