If you are searching on co.com for reward seats make sure that you are not logged in to your account. As a CO Silver you will see additional coach reward seats that are not available using your BD miles.

Otherwise the above answer is pretty much complete. There is no way to know when the seats will show up. You have to keep checking to find them. And the TLV-EWR route is notoriously hard for reward seats up front.

Good Luck!