EmmaBetty:
1 & 2) You are dual-status, but you can file Form 1040 or 1040A as a resident alien because you meet the Substantial Presence Test.
3) You will need to attach the statement.
4 & 5) You probably could file jointly with your husband, but his Chinese income (wages and interest) would be subject to U.S. taxes. You will get a credit for the Chinese taxes paid, however.
6) You may be able to get the withheld Social Security and Medicare taxes back by filing Form 843. I do not think filing as a resident alien takes that right away from you, but I am not sure. You may want to post your question on
www.thetaxguy.com. He specializes in taxes for non-resident aliens and has a lot more experience than me.