The router has nothing to do with the issues you have.
What are the LAN IPs for the router/modem and for the ASUS router?
On the ASUS router - LAN -> LAN IP -> IP Address
How is the Internet connection configured?
On the ASUS router - WAN -> Internet Connection -> WAN Connection Type
It's getting late here, 11.30pm... someone else will help you further. It's just a router, don't get stressed out.
Yeah you're right, it was 4am here so I was just frustrated.
Still can't get the router to work, even seeing the menu is a chore, and while setting up it can just drop the connection, so seeing all settings is hard too.