In wordpress.com the 3 column themes are Andreas 04, Andreas 09, Fadtastic, Garland, Sandbox, and Twenty-eight Thirteen. There really doesn't appear to be any crossover with the custom header list. Looks like Sandbox with one of the custom CSS designs might be the best bet.
I am really embarrassed by my lack of knowlege and inability to articulate what I do kind of understand!
I have two underdeveloped pages that appeared in some of the themes and not in others. I have tried all of the theme's that are currently available on wordpress.com without CSS upgrade, hence the page comment. I'll need to do a little more reading from the link on those to try to understand why or how they may have just been displayed differently.
I printed out the page on widgets. In my earlier post today I described not understanding all of the different kinds of widgets and I plan to read the printout.
I must just have some blog-design envy from many of the blogs I've visited :) but clearly it is something that I am just going to have to get over!! Thanks again.