Does that mean my hacked account can never be recovered?
At the current rate it's unlikely to be recovered. If you check the other threads in Meta even accounts with signed messages aren't getting restored or at best they have to wait weeks/months. Accounts could be restored by doing a bit of investigation on IPs etc but it's not foolproof and the forum currently doesn't have the manpower unfortunately.
If that's the case, then by right my account should have extremely high chance of recovery if the admin care enough to look into the IP addresses used.
I don't understand why email address can be changed/edited.
If it is a security vulnerability, then by right it shouldn't allowed to be edited.
This would probably have prevented a majority of all the hacking, but why isn't the admin doing it?