Cisco VPN :: 5505 SSL VPN Works From Inside But Not Outside

I'm setting up a VPN in order to share files between two locations. I'm not sure it's the best solution, but he insists on using his Cisco ASA 5505 Firewall via a clientless VPN. His set-up is a simple residential cable modem (Motorola SurfBoard/TimeWarner) set in DMZ mode, the Cisco ASA, and an Ubuntu server.
 
The Clientless VPN is set up, as are the user groups, and bookmarks. I'm able to browse to the firewall's internal interface IP (https://192.168.1.1) and log in to the Clientless VPN portal, and from there, I can access all of the plug-ins I've configured (CIFS, VNC, etc). The problem is that I cannot connect from outside the local area network.
 
I think it's something very basic that I'm missing, like a NAT rule. I've tried adding some, but they always seem to interfer with the NAT rule allowing users to connect, via the internet, to the Apache web server (port 80) running on the Ubuntu machine behind the ASA Firewall.
 
Like I said, I'm not sure this is the best solution for him. Using an ASA seems like overkill for something that can be accomplished with some software, but he and I are both fans of Cisco, and, as I said, he is adament about using this set-up. If it comes down to it, I'd like to be able to honestly tell him that I exhausted every resource in trying to find a way to make this work for him before giving up and going to "Plan B".