MT and two public IP

My ISP gives me two public IP addresses, so I try to use them both.
I would like to configure the RB433 as pictured.
The problem for me is to configure the MT, the server receives the IP address from the modem.
Or as an alternative to set the DMZ for the server. But the DMZ configuration examples I found are made for static addresses.

I tried also to set a bridge between ether1 and Ether2. Then server received an IP from my ISP, but, on the other interfaces there was no Internet access. Masquerade set to bridge or ether1 did not work.
I am a beginner so I will be most helpful if get some programing examples.

If ISP assigns both public IP’s dynamically, then you have to have two network interface to be assigned to.

One solution is ti add switch between cable modem and MT and connect server to that switch, which will allow it to get its own public IP.

The other is to use two network interfaces on MT connected to cable modem so each would get it’s own IP, and then do DMZ thing for server.

Could somebody give me example setup for DMZ when public IP is variable?
The all exampes which I found look as they were made for static IP only.