A DMZ is used for machines that you want open to the Inet for the most part but are still secured to some extent. For instance a DMZ is a good place for your webserver and any front-end applications you may have the need for internet access. The DMZ is usually situated as an extension off of your firewall. Either one port or just an extension network. Most DSL routers don't do DMZ stuff so tell me what the equipment is......that'd help.

The rest of your question I can't make out, why don't you try one at a time...

peace