1. All the Denon receivers I've ever owned don't have such a setting. It will work with any combination of speakers.
2. I'm guessing the receiver should have the Audyssey mic setup, which you should run. That will give you ideal settings for speaker distance, crossover, etc. But if you do it by ear, set the speakers to "small" and start around 80hz crossover.
3. Not sure but I'm sure a Google search might help. b) since your receiver will be handling the bass management, you normally get the crossover setting on the back of the sub out of the way, or to the highest setting. The crossover settings for each speaker on the receiver will direct the low freq's to the sub, below those points you set, or Audyssey.
