If you still have the old one it MAY be rescuable by the sequence of "factory reset, flash new firmware onto it". Still doesn't excuse the the software design (which is basically down to "USB drives have to present as floppies with a FAT filesystem, so the only way to be sure they're in a consistent state is to flush the entire state and stop allowing modifications") and definitely does not excuse the screen breaking.

My first Kobo had the "half screen is off" and I think it was down to it being under pressure with a paperback across half the screen, causing it to bend. Over a period of about half an hour, the broken part of the screen went from "looks faint" to "completely white, no changes visible".