Your responses are so helpful, thanks. Often1, you're absolutely right - there's no point in arguing with front line personnel. They won't do anything more than offer me (1) reimbursement for the ORY-SFO leg or (2) a rescheduled 5/18 ORY-SFO flight.

As irishguy28 points out, Article 8 says that I should have been offered "re-routing, under comparable transport conditions, to their final destination at a later date at the passenger's convenience, subject to availability of seats" Practically speaking, I'm unlikely to get that option before the 5/18 flight leaves, at which point, it becomes too late to get any type of reimbursement. Considering the language of Article 8, which states that "passengers shall be offered the choice between" reimbursement, re-routing at the earliest opportunity, or re-routing at the passenger's convenience, BF has already violated the provision regardless of whether I take the reimbursement simply because I explicitly wasn't offered the third option.

Once I figure out how to fly back to SFO, what's the best route to take to hold them to EC 261/2004? BF customer service hasn't been effective at all. They've refused to give a reason for the cancellation, either lying about it or telling me "you don't need to know," and have repeatedly told me that I have no rights under the regulation.