autofire = hold space, click outside the game, release, click back to the game. I know, it's just one key, but.. hey, it's one key less :P (I discovered it after finishing the game, for the record :P)
To get the "My Precious" achievement I waited for all the enemies to spawn, taking some down from time to time, very carefully, and then killed them all.
It is not easy to browse through your cards to select them for a deck. It would be nive to be able to sort them out in different things (other than the ones already there), and like checkboxes/multiple choice (Gold/Souls/Crystals/Iron to cast, *Race*, number of spawns..)