I don't need to set the Xbox in the DMZ (which I tried before when it would take a long time to log in and it didn't make a difference) due to me forwarding the proper ports - which made Live log in damn quick. And I don't like using UPnP - never seemed to work properly for me.
Actually, I did manage to resolve the issue and I think it is a bug in the DDWRT firmware (which I will report). I initially had the bridge hold a static IP, and it would connect to the WLAN and I could access it and everything. But it never showed up as a wireless client in the DDWRT. Well, I figure I'd try a shot in the dark and set the bridge to get an address from the DHCP. After that, Xbox live logged in in a mere 30 seconds or less and it showed up as a wireless client. This HAS to be a problem with the new firmware.