First suggestion: Don't cross the border when you are adjusting your status,
otherwise you will have lots of trouble.
If you can't postpone your departure date, you have to stay in China, until
your H-1B petition gets approved; your employer's attorney receives USCIS'
approval notice and Fedexes it to you;
After you receive the approval notice, you then can use it to apply for your
H-1B visa.