Fixed it!
I uploaded the new firmware
.bin via DIAG mode's "(USB EXPORT)-USB device mode" and then rebooted the device. It updated and started working again!
Any pointers now on how to jailbreak it via SERIAL since I have it already hooked up?
I noticed that the "Diag" menu is different on the device from the one that is mentioned in the serial jailbreaking for dummies tutorial
https://www.mobileread.com/forums/sh...d.php?t=267541