The problem you are going to have then is that if you do not have public IPs on both of its interfaces, you cannot use the internet because the private IPs you can use are not routable over the network.
Sorry but this is not correct. The Mono is still performing NAT. The problem is the rules on the mono. You have allowed your LAN out, but to the Monowall, it's LAN network is 10.0.0.0/24. Your simplest option is to replace the Linksys router with a network switch. However to get it working with your existing setup, what you need to do, is first add a static route on the Mono to 192.168.11.0/24 gateway 10.0.0.40 and also enable "Bypass firewall rules for traffic on the same interface" in the advanced page. Next you can add the rules to allow and block your traffic, but you will have to enter the network manually rather than picking LAN network from the drop down.