You are using a resolution that didn't exist when the game was written many years ago. They did introduce an experimental scalable UI (not just font) so you could try that at various settings, usually somethign between 1.2 a nd 1.5 would be right.
Alternatively you could check for font mods , there used to be one call Better Font Mod, something like that.
Failing that reduce the game's resolution to say 1920x1080.