- Changing email address of the account to the unreal one, therefore no one can use the unreal email address to recover the account later.
this won't prevent recovering the account using the original first registered email address cmiiw, manual recovery hacked account can be initiated by request from original email address
It seems your request has been fulfilled 
unfortunately all his posts quoted by others still bear his original username 
You might want to remove the screenshot from the first post and perhaps lock the thread.
and he needs to edit/remove a few posts that still contain his personal details in one of his posts in lending section he listed his website, google+, and facebook account