I know I didn't want the content to wrap around beneath the sidebar after the sidebar finishes

That's easy to avoid by putting the content in a div whose left margin is wider than the sidebar. It can still be a %age of page width (the margin, as well as the columns). I think IE7 even honours min-width, though earlier versions of IE certainly don't.

(alleged) higher weighting for terms towards the top of the page

I don't think your sidebar has enough content to make it worth worrying about such factors, if they even exist.