Can't get extra_english.lang to work

[Your Computer]

Once I undid the changes in the tutorial I mentioned and made a new profile, the lang file was working successfully.

However, once I changed the main_setting.cfg and user_settings.cfg to quick load the map, it stopped working again. Should I be going about this a different way?

You've come across an issue that is known but one that not every one has. This means you're going to have to test your map without developer mode.