Well glad it get fixed *eventually*
The best part of trying to help is that I also learn along the way, in your case .
To Reset the Tablet to Format the Factory Reset Protection (which does not show the old google account) is to simply install a Custom Recovery and once that is done , format the frp partition.
You may select the above answer as "Best Answer" so the question is marked as "solved" and it might help others aswell :)