I am trying to flash my backup ROM – but when I click "Restore" in TWRP, it doesn't find my files! What am I doing wrong?
TWRP has a file manager by default in Advanced section... I'd suggest that you do a backup as is, and then use the file manager to move the Backup in exactly the same place that TWRP just made !
Make backup 1
Move backup 2 to backup 1
Restore backup 2