My local range has an "open range" where I can set up multiple targets, rapid fire, etc...

What distance should I spend the majority of my training at?

My this, I mean at what distances are MOST defensive shootings going to take place?

Of course I will spend SOME time at ALL distances, but I want the majority of my time spent and the most LIKELY distance I would have to defend myself from.

Two yards out to ten yards, and everything in between.  Practice a lot of shoulder point, no sights, at the closest ranges.

Try some of these:
www.sportshooter.com/improving/drills/