There’s no single setting that every product just uses? I would think that there should be a way to set a default theme for a product’s view and having an individual setting for each product is just a way to override the default.
I found a tutorial video on this site last night that showed going to a different place to set the theme. http://www.hellothemes.com/blog/installing-hellotheme/ In this, instead of going to the Design section in System > Configuration, I went to System > Design to add a new Design Change. I then removed the original config in System Config > Design. This worked, but only half way; it only affected the Homepage I set up. The product pages still used to default Magento Demo Store template.
So now I went back to System > Config > Design, and reset all the theme options to “hellouno”. Now it looks like the product page is attempting to work. It appears as if the background is still Magento default, and some CSS isn’t getting loaded to make the page display properly. Here’s a link to see: http://goo.gl/mhGTb
I refreshed the cache along the way, so I don’t think that’s an issue.