I managed to get to downgrading and rooting the phone, but after apparently flashing cwm through rom manager, I turned off the phone and tried to boot into recovery by vol down + power. Those are the buttons I use to boot my g2x into recovery, and through searching I didn't find any other combos for the g2.
That didn't work. I got sent to fastboot again, and no buttons work. I then tried RUU again, and this time it worked, booted. I turned it off and back on to see if it would actually load the rom this time. Alas, fastboot screen again. Still no working buttons.
I tried the PC10IMG.zip again. It flashed, but when it says <Press power to reboot> and I press power, I get sent to fastboot.
I pretty much consider this phone a lost cause, but if anyone has a suggestion that might help, please tell!