How can I present evidence at a review hearing without filing anything with the department/court?

It is unclear what exactly is going on.  Normally, you do not present evidence withouit it first being disclosed; here, of course, you assert that the information in question is known to both sides; if you don't want to disclose the extortion material itself, simply refer to it as such, and offer to submit it under seal for "in camera" review if the court really wants to see it.  You should almost certainly consult counsel.