In regards to the missing thumbnail are you setting any of the columns to the name of the image? This is the trick for getting this to work, you would have the image name stored in the cart, then in the cart display you make sure that the source of the image is pointing to your images folder then you use the binding for the image name to have it show.
What you have described for your details page is called a master-detail page set. The idea is that you link to the details page with a unique identifier like the items id. Then on the details page you would have a recordset that is filtered on this unique value. You can then use the recordset bindings to show any of the details about this new item.
As for Menu Writer you can craft dynamic links to go the various pages for the different categories. You should take a look at the support page for Menu Writer. If you have only the dynamic suite you may not have this tool, check in your download center to confirm if it is available to you.
