Well, first you need a new recovery from today. The link is in the PM that I sent you originally.
Take your decrypted update.zip (You have used DeBooxUpd.py on the .upd file, right?)
Put it on a flash drive in the root directory.
The flash drive should be formatted with normal "Windows FAT."
You just need to fastboot boot p9mod
It will have the splash screeen saying "Onyx".
Wait until it turns all white. (Even though your PC has bonged to show you that ADB is ready.)
When you do the next step, keep your eye on the display. It should flash white/black/white. If it doesn't, stop right there.
Next:
It should say "Waiting for flash..."
Disconnect the USB cable from your desktop.
Plug in the OTG adapter/flash drive and cross your fingers!
Within 3 seconds it should start automatically. Keep your eye on the display. Use a camera to capture any error messages. It may be that we have to add a symlink or something before we run the updater.
Good luck!