Dear xdai:
Please read my posting very carefully, I haven't said anything contradictory. I don't blame you, the subject matter is very confusing. In the sentence,
"Based on what I know, you should wait at least till you get your EAD. Once you have that you could switch employers provided your 485 is pending at least for 180 days, which in all probability it will."
It doesn't mean that you should wait to change jobs till 180 days have elapsed since you filed for 485, it means that your 485 should be pending for at least 180 days past the date you file for your 485. Did you get it? If not, let me know.
Regarding your questions,
"Let's put it in a simpler way, if I change job (voluntarily or involuntarily) before I-485 is pending for 180 days, will my GC application become void? What kinds of choices do I have in this case?"
No, your GC application does not become void. That's the safety net that the 485 process provides. Your choices are to find another job as soon as possible in case you're laid off, in a same or similar category. Then wait for the 485 approval. If you do get an RFE, you can always provide pay stubs, employment letter, etc. from your new employer. If you don't get an RFE, then you're through if your 485 approval comes. That's it!
Best of Luck!!