The readability unfortunately cant be fixed without a major design change (which I don't want to do), or going into about:config (which is scary).

By sheer coincidence there's a theme that came out before this one was big that's essentially exactly what you're asking for. Here's the link:

https://addons.mozilla.org/en-US/firefox/addon/red-gaming-theme/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search

This was intentional. I've gotten an email asking for a white background, so I made a version with it and then switched it back to dark in the next version so people can choose which they want.

You should be able to fix this by either re-installing the theme, or by selecting the newest version on the sidebar

The red font is definitely a stylistic compromise, but I have managed to fix the unreadable taskbar. I've got the instructions in the theme description, but I'll paste them here as well.

Be careful while doing it though, because the menu you have to access can mess up the browser a lot

1: Type " about:config " in the URL bar

2: Type: " browser.urlbar.formatting.enabled " in the provided search box

3: Click the Plus Button on the option

4: Click the switch button to set the setting to false

Try this theme. It's made by a different creator and is basically a muted version of this theme.

https://addons.mozilla.org/en-US/firefox/addon/red-gaming-theme/