C7100V issues -- mainly with router

I'm using this Comcast-specific model (with telephony). I first used it in Gateway mode with my ASUS router. BUT, when I tried to update the firmware of the ASUS over the net, the router wouldn't connect and the C7100V went into outer space, with nothing connecting to the Internet any more, even after repeated reboots. I removed the ASUS and am using only the C7100V (in routing mode) to simplify troubleshooting. After several factory resets, many reboots, a lot of hair-pulling, and hours of configuration, it's mostly working.

 

My main questions:

 

1. Anyone who has set up the C7100V as a gateway, can you offer tips on configuring an attached router (in my case, the ASUS) to avoid the problem I had? (Maybe something about netmasks/gateways etc?)

 

2. Whenever I add or remove a device to/from the C7100V's reserved IP list and reboot the device, it shows up as 0.0.0.0 on the C7100V until I remove the battery from the C7100V, unplug it, plug it in, and let it reboot. (0.0.0.0 on a client means no connection.) Anyone else have or solve this?

 

And minor ones:

 

3. The Web app to control the C7100V times out WAAY too quickly. I find myself having to log in constantly. Is there any way to change this?

 

4. The DHCP servers in some other routers give each device the same IP address each time it connects, even without a reservation. My impression is, the C7100V picks a new address each time unless you have a reserved IP. Am I correct?