EXCLUSIVE: The Academy Awards looks to be going without a designated host on Sunday for the first time since 1989, but broadcaster ABC had to break some new ground this year in the era of plummeting ratings. Even before the host and category chaos that have hobbled the ceremony in recent weeks, the Disney-owned network found itself forced to guarantee a ratings threshold to keep the deepest-pocketed buyers happy. "The Oscars are still a very big deal but people aren't…