No Title
To clearly and completely answer your question, someone need to write a book about it. I am not exaggerating, believe me or not. Even a book will not completely answer your questions, since there is no INS regulation to implement the relevant law. Not to let you be disappointed, I will try to answer your question in general terms but be aware, it is not a accurate one and nowhere close to the final decision by INS. And I also recommend you to read some excellent liberature freely availabe on the web to educate yourself on immigration issues. There are:
www.immigration-law.com
www.shusterman.com
www.ilw.com
......
Here is my try:
Do you have to have a "similar" job if you have been laid off after 180 days (on your I-485) or you can work at any McDonalds until you find a decent job.
Answer: Similar or same profession according to AC21. You can work at McDee any time if you have your EAD. However, at the time INS ajudicate your case, if being asked, you need to provide evidence to satisfy you are in the same or similar profession as in your I485 application.
Does it mean you can NOT stay "lay off" (then whats the advantage of 180 days
If your company informed INS that this guy has been laid off, will they stop processing your I-485.
Answer: See answer to your first question. If you lost your job after 180 days, it does not matter if our company notify INS or not, as long as you meet the reqirements (see answer to your first question). If before 180 days, if your word "notify" means company withdraw I140, you risk INS deny your I485 application.