I will arrive in Beijing via Nanjing on China Eastern from Australia -

I believe this will arrive in T2? I then need to go to T3 to catch a flight with S7. The time between the two flights are 3 hours from midnight. A few questions please;
1. would the T2 to T3 tranfer be considered I->I considering there was stopover in Nanjing?
2. would there be sufficient time for the transfer?
3. Do you know if S7 will depart in T3 East or West?
4. Do I need to go through customs checks twice?

Thanks very much.