As you said - point 3 is a problem
Well, a shopping cart that logs the user out of the whole site is not much use.
Let's put our trust in WA to provide a solution.
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.