What I ended up with was this:

font-family: verdana, arial, helvetica, sans-serif;
font-size: .9em;

I have a thing about the Verdana font, I just like it better than arial. I tried 12px and it looked good but the text crowded in on the images too much; the .9em font size was the result of some experimenting (I started with 1em) and that's what's there now. I could go back and try 10px and see how that works. I don't seem to have made very good notes but I did note that "1em doesn't quite clean up the display in checkout_shipping."

Trouble is, although the site looks much more similar between the browsers than before, the fonts on the checkout_shipping page are MUCH bigger than they should be. They seem to be being sized independently of the body {} settings and I can't find where.

It also bothers me that the text disappears behind the right pane instead of "realizing" that it's out of space and wrapping to the next line. It's acting as if it has a fixed width for display - is this a side effect of a fixed width template?

Your advice is GREATLY appreciated!