Isn't the Default Gateway IP Address determined by PPP connectivity? If the 192.168.254.254 address is to log into your modem, that might be what that is for but I think that can be left blank since it is most likely talking about the Frontier edge router gateway address (which is usually a Public IP address, not a private one). Everything else such as the PPPoA and VC settings appear correct to me. I'm not entirely sure as to what that ATM Interface setting is. -- Here comes the white stuff which falls from the sky during the winter again!
For the ATM interface: VPI/VCI = 0/35 Encapsulation = PPPoE LLC (PPPoA should work also) DHCP should be on - you want frontier to assign you a public IP DHCP will also push the DNS addresses to you as well.