5. For sim cards, I think Unicom is a safer bet than Mobile, and data is insanely cheap
6. Register for Wechat and Alipay with your China phone number
7. If you are going to be in China often, open a bank account at CMB or ICBC

Eta: 5 and 7 are definitely annoying, but if you can endure the bureaucracy, things will be great for you