I don't want to let sites choose fonts, but when I turn that off I lose most icons, video player controls, etc.
When I uncheck "let websites choose their own fonts" I start getting garbage in place of icons and special characters. How do I get the fonts I want and also the special characters or icons?
Opaite Mbohovái (1)
The problem that you are going to run into is that most modern websites use special font packs for their icons instead of image files, which was previously the standard. Since you are preventing the websites from loading their custom fonts on Firefox, you are also preventing them from loading the fonts that contain those icons and symbols.
Unfortunately, since Firefox doesn't analyze what fonts websites are attempting to load, when you select that option, you are going to face this issue.
Sorry.