There are a few things,
1.- Again, modifying core files (while possible) is not encouraged, it could be done with a plugin, in fact, there's a
free plugin that does exactly that : More edit
https://market.osclass.org/plugins/ad-management/more-edit_23 (it's a bit old)
2.- There are two different attributes for a listing active/inactive & enabled/disabled, both have a 0/1 value and are similar but the different is quite big.
Users can change the state from inactive to active, but
can not from disabled to enabled, only admins could do both. (I see you got this ok, but just want to remember it)
3.- Use brackets, really, use them
Instead of this :
if($this->is_admin) $enabled = 1;
else $enabled = 0;
write this
if($this->is_admin) {
$enabled = 1;
} else {
$enabled = 0;
}
4.- Don't modify .po nor .mo files directly, let poedit parse the sources and get new strings. I know, in this case, this is the only option since the code has a text different than the one it should, but it's a bad idea to modify .po / .mo files
Take a look at more edit plugin to see how it could be done without modifying core files