Cynthia from US Air called me and stated that they will now waive the $150 change fee (the letter I posted earlier today said that they will not waive the change fee). So, I've booked my new flight going through a scanner-less airport*, but had to pay the $100 fare difference and will also have to (as of now) pony up for the one-way rental car.
*In case you're interested, Allentown, PA, Atlantic City, NJ, and Norfolk, VA are the nearest airports to DC that have no scanners. All are about a 4 hour drive. Let me just say that if I were not going clear across the country, the amount of time I'll be investing in this trip would not be worth it.