In my regedit i changed everything to get office 2010 working with the online editing feature:
Modifying the registry with the following keys: "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters\BasicAuthLevel" 2 “HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Common\Internet\BasicAuthLevel” 2
Are you able to use the dyndns redirect inside your network too? The problem appears to be that on the port redirect to 7070, it goes to the alfresco-global.properties setting of vti.server.external.host (see: http://docs.alfresco.com/4.2/tasks/SharePoint-config.html), which is set to your internal name. The server really needs to be addressable by the same name both inside and outside your network to avoid this type of problem.