Did I kill my board? Is there anything I can do to try and recover it?
Try a different USB port on your PC, or even better a different PC. You may have damaged the USB port on the PC by drawing too much current. The Arduino board has a 500ma polyfuse that tries and protect the PC's USB port from overcurrent but it's a slow acting fuse, and perhaps your PC usb has an internal protection fuse that blew open first.
Lefty