While formatting with twrp results in an error, formatting with fastboot worked for me:
start phone, which will boot into twrp
reboot -> bootloader
fastboot format:ext4 userdata. This will of course delete all data from the phone.
This answer isn't immediately applicable to OP's Nvidia tablet, but I'll leave it here in case it's useful to others.
https://mirrors.lolinet.com/ hosts many Motorola stock ROMs. I don't know if the site is trustworthy or not, but I'm using it now.
After you download a stock zip, use https://github.com/dlenski/motoflash2sh to generate a flashing shell ...
I think thing the best course of action would be to download and install a third-party Android Emulator. If you are on Windows, I would recommend Bluestacks. As it can be easily rooted with this tutorial here. If you need any help, feel free to reply to this message.
Hope this helps you out!