These topics have been addressed in the forums.
Allowing LuCI / SSH from WAN is recently discussed here -- this is a bad idea if the router is internet facing, but you have stated that you are setting this up on a private network behind another router/firewall.
and if you want to make your own default settings (so that you don't have the 'standard' default settings when you reset the router), you can build your own image, discussed here with links to the wiki for implementing it.