Just a comment on the font-size issue. Sorry if this has been said elsewhere, but I couldn't see it.
I have found that the minimal change to the .css files is to delete the lines
Lines that define other sizes, for example:
font-size: 1.5 em;
are useful and do do not cause me problems
If the font sizes are defined in points, then I convert them to em using 12 pt (or occasionally 11 pt) = 1 em.