You are probably fine
While you should really consult with an experienced immigration attorney (you only need maybe 30min to discuss the case and the money for a consultation is well invested), from my lay-men\'s point of view, you are probably fine. If you read this board, you\'ll notice that several people are in a similar position to yours. As long as company A offers to hire you back after approval of your GC, you can continue the application through them. If the I485 approval takes longer than 180 days, you can even switch the application over to company B without any problems. In any case, you make your life easier, if you get an EAD (even if it might be advisable to not immediately make use of it; just having the card in case of unexpected emergencies is probably a smart move).
Good luck, but don\'t worry too much -- and please, do talk to an attorney.