I may have missed this...
I may have missed this in looking at you code but...
When you added your add to cart button to the page, did you designate a URL in the general tab "redirect" section of the add to cart button panel?
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.