If USCIS send you RFE for employment status in US, I may got trouble. I still don't quite clear? My question is if the employment status is valid for me to work for a US company in its foreign branch office. The US company should have a job offer and job verification letter to show I am employed as an employee for them but work place is in a foreign country.
-Then, it will be fine, but you may need to stay in US physically in this case because I-485 is for the person lives in US to adjust his/her nonimmigration status to immigration status. So, USCIS may ask you to apply for the immigration visa in China if they find that you are working China. Thus, you will take a longer time to get the green card. Of course, what I said here is just a possibility and may not happen in reality (you may not get such RFE).
Another issue is that you need to have the Advanced Parole (AP) to go to China and the AP is only valid for one year (you need to return to US before the AP expires). If you travel to China without AP, your I-485 will be invalid. So, how to you work in China for a longer time (> one year)?