We do offer support, our free support covers helping with common problems through our forums and e-mail. If there's some specific problem which can't be replicated on our test server and is not reported by anyone else, we provide a paid support service to check the problem directly on our customer's server.
Thank you for the screenshot. It seems there are some SEF URLs created correctly, so there is probably something special about the ones that aren't. Could you post a screenshots from your JoomShopping administration for product with ID 2 for example? Thank you.
As regards adding the "www" in front of your subdomain, that's usually caused either by the .htaccess file or by the "www and non-www domain handling" option in JoomSEF's Configuration on the Basic tab.