I don't know how much you

make in U.S. If the difference is less than 30%, I guess you should stay. But it also depends on which way is better for your career advancement.

You cannot get GC by just coming back one/two times with AP. I-140 is not forever, but it can last a reasonable time (depends on the conditions of approval isn't changed). Maybe 1-2 years.

Actually you can send letter to USCIS and ask to change from I-485 processing to Consular Processing (Get immigrant visa from oversea U.S. consulate). For example, change to Guangzhou, China. Tell them a job need you badly in China and you should also confirm that you will be back U.S. once immigrant visa approved.

You can get both of job and GC by this way. Consult attorney if you're still uncertain.