.htaccess cannot affect page content, not even meta tags.
To change the back end title, just hook the ‘admin_title’ filter and output any title you like. The admin and non-admin titles are passed to your callback if you want to use any of that for title content.
The code for this sort of thing is is best placed on your common cross site plugin that contains all of your handy customizations and useful functions for all of your sites. If you don’t have one, perhaps it’s time to start 🙂
You are right! Good advice 🙂