Thanks, fassy. Expedia advises I wait until I complete my departure flight, then I should pursue changing my return flight. They say if I try to make a change to my return flight now (before my departure flight), they'll need to "reprice" by round-trip ticket. They estimated I'm looking at an additional $1,100 to do that.

I was able to find a new one-way return flight for $760. I'm considering grabbing that and just being a no-show on my original return.