RE: Dell XPS12 Messed up during A08 BIOS update
Are you seeing anything at all on that system? Nothing on the screen at all? What about any beeps coming out of the system? Check out this support article for the XPS 12 and see if it helps you at all.
Unfortunately, you've listed all the things that I can think of offhand to try to get the system working again. But there may be something in the article linked above that may be able to help. Is your system still under the original Dell support warranty? I'm assuming it's not or you would probably be calling Support already.
Sorry I wasn't of more help.