Problem with Font Settings panel

I want to change the default font for page content from a teeny 9x to 10x, or maybe 11x.

I found the Font settings page in the WP Dashboard (Appearance > Theme Options > Font Settings) which provides a panel for “Content Font” which I assume is the relevant option.

In order to make any changes it seems that you need to check the box at the top of the page to enable custom typography. However, when I do this I discovered that the default font settings for all of the fonts (Content Font, Navigation font, Widget Areas Font, H1 Heading, etc) are actually quite different to the fonts normally displayed for the theme. Clicking the Options Reset button at the bottom of the page doesn’t change this.

AND, to cap it off, I found that the one font which I did want to change, i.e. “Content Font”, actually stays the same as the normal theme font no matter what font size I set for Content Font (which was kind of amusing in a perverse sort of way).

So, How do I increase my page content font size without screwing everything else up?