Do Magic and Faith Dice ever get used up? And can you try to Dodge every attack that comes your way or only once a "round"?
Magic and Faith Dice do not get used up. They do have other resources tied to them, however; Magic incurs Fatigue (and that is a limited resource), and Miracles 'cost' Willpower.
You can technically only be in 'dodgeable' situations twice per round, as all attacks against you are 'summed up', and only the highest damage roll is used. Rounds are split in 'quick turns' and 'full turns', so there are two situations in which you can take damage that is dodge-able. There's no explicit rule forbidding multiple dodges. Dodges also incur fatigue, so I'd say dodging multiple times is allowed.