When you run out of City Tokens/Districts, you cannot explore or expand more. While you can destroy buildings to make space for new ones, you cannot destroy Cities or Districts to use the tokens elsewhere.
Yes, when you run out of cards on the last round, shuffle A,B, and C together and draw the remaining cards.
Awesome Thanks Ryan. Great game I have played twice and really enjoyed playing it both times. I don't have other games on my game shelf that are like it. Going to add Expansion Town Cards later tonight