You should be able to go backwards in version using LG Flash Tools and the tot/dll method. If you'd like to try that, here's files you can use:
Listing of Stock_Firmware
Last 2 are what you want. The large zip contains the tot, unzip to reveal it. I'd use the dll there too (last file in that list). These are indeed older files but once you get a working phone, you can accept OTA's to get back the rest of the way.
Here are the general instructs to using this method, you may have alternate instructs you want to use and that's ok too:
Restore Stock G2 Firmware - Pastebin.com
Make sure you are using the version of LG Flash Tools which is linked there. If yours is different, use this one instead. You can obviously skip the part to download the tot/bin as I already linked that above. But there's a nice link there with additional instructs which have pics. That's a handy addition.
Also note the part about replacing the megalock dll, that's key. You can try the one linked in that tutorial first, if you get any megalock related errors, use this one instead:
Alternate megalock dll
Thanks to Autoprime (xda/freenode/codefire) for the files and writeup.