The font size saga continues...
Font size has always been the something Im still yet to master, but what I would suggest you do is to look at using rem units for your font size instead of fixed pt or px, assuming that's what you've used. rem units relate back to the root font size, by default this is 16px. However, you can change this using css using a media query to change it based on the size of the screen. Therefore if the screen is large, 1rem might = 16px, but if small, 1rem might be 13px.