My EAD has almost expired in Feb, and unfortunately there wasn't even 90 days after I submitted renewal and before it expired. And I can't event get any interim EAD before the 90 days.
I asked several sources, company lawyer, outside lawyer, friends... identically, the answer is I can't work or get paid (including paid leave) before I get the new card. There was only one lawyer said unofficially that I shouldn't even have told my employer if they hadn't found out themselves.
As I later knew, the new EAD card will always bear a continuous starting date with your previous one, even it's approved months before the expiration date. In another word, if your employer knows you don't have a card, they are not supposed to let you work. But on your record, no matter when you get the card, the time will be consecutive. Luckily, in my case, my renewal was approved on the day it was expiring. But unfortunately, I haven't got my actual card yet due to the mess up in CIS for my address. (I posted in another thread, please help.) My employer is ok with the printed approval notice from the website for now.
The lesson learnt, better submit it earlier than later.