Total guess here, but maybe the phone mounts the SD card on boot and those files are configuration files, and when you edited them you basically fed the phone garbage and it stalled in the boot process. I don't know if that's bringing you much closer, but maybe you could hack something up that'll take advantage of that mount and let it load something on the phone? But unless you knew how the OS worked I doubt that would be an easy feat.

I'd go with another phone.