2 things:
- No-ip offers you nothing more then DynDNS, so when DynDNS is supported through the webinterface, why not use DynDNS instead?
- You do not need to forward ports or place anything into a DMZ to get the FTP server running. Disable Virtual DMZ, Virtual Server and Port trigger, enable the ftp server and check if port 21 is open using ShieldsUp!. If it does not show up open, then consult your ISP website to see if they block standard ports like FTP, SMTP or HTTP.