I finally upgraded this site to the latest version of WordPress. Although it was not strictly necessary, I completely recreated my theme from scratch based on the new default theme, so some parts of the site may be a little strange looking. If you see any weird problems, please post a comment here.
Update: I have also added style definitions that should make the pages more readable on mobile devices (where previously they were illegible). Unfortunately, there is not much consistency for style support in mobile devices, so it may not work for you. Leave a comment if you have an issue on a mobile.