Hi.

Yes, you got root permission, even in your first attempts (I didn't notice )...... so I'd advice you to follow peterleinchen advice and maybe check that the commands tune2fs and sfdisk are in your system. (I can see them in your execution log).
I'm not a Linux Mint user, but provided that Linux Mint is Debian/Ubuntu based these commands should be in your system.

Also, if you take a look at your /tmp/ directory files while flasing is in progress you may get some more clues....

Good luck.

Regards.