Now that I think of it, rerolls are simpler if you can use them on any dice, but it will work better with the expansions if the sword doesn't allow rerolls on one-use dice and spells.
Michael - A skeleton key is not equipped, but is a bonus die that may be rolled once per locked chest.
You cannot use an ability from a drained die, but you can prevent your opponent from using the ability in time. Really, this rarely seems to happen.
You cannot have negative level dice. I realize an error in the wording though. The wound from ghosts and the healing from slimes only results upon defeating the monster. I've tried wording this multiple ways and it always ends up creating some new confusion. Maybe I should just list the effect on the reward side of the die. I could do the same thing with bonus experience and reduce some of the clutter.
All good questions, and I will make sure the rules/FAQ address everything mentioned in this thread.