Toolbars: I want to increase the font size of the top header text, specifically the bookmarks toolbar, search bar, and tab titles. The text is too small for me to read.

The following answer may help. If it doesn't, you can create a file userChrome.css to set font sizes. The setting ''layout.css.devPixelsPerPx'' also affects the size of content in web pages so you may need to change your default zoom setting to offset that. https://support.mozilla.org/en-US/questions/1415257#answer-1584444