you must have a replacement fixedsys font, as mine only allows me to select 9, and you have 5 and 7. As for the toolbar, you can adjust this here:
Alt+o -> Display , right hand side is a dropdown labelled "Buttons:". Switch this from small to large.
I'd recommend choosing a new default font to get larger text. Lucida Console is a rather nice one, still fixed width like Fixedsys with much larger ranges of font sizes.