John, Not sure i´m on the spot here but to spread your products in a two-column table when looping through your items check out the {delimiter}-operator. Take a look at sitemap.tpl to get at grip on looping, tables and delimiter.
Some pseudo-code to give a hint could look something like:
(I have not been working with the shop-module so maybe the fetch-things are not relevant here but the delimiter-thingy seems to be what you are looking for)