I believe the post you need to do should thoroughly explain this part of the above challenge as it is the key to the security you are highlighting.
" Luckily, I still had an EOS OWNER key in my possession, linked to a different EOS public/private keypair ;-)"
And maybe a well written tutorial on generating safe key pair and new account linked to an owner account. I am considering changing my genesis accounts key pair for this very reason. if i did i would use this tutorial from gerereos
https://steemit.com/eos/@genereos/eos-how-to-quickly-and-safely-change-your-public-private-keys