And now your pfsense thinks it has a WAN connection going to your gateway device "My Modem".. No modems have seen have that IP ;)
Dude I am not talking about a portforward, I am talking about an outbound NAT from your lan to your new opt1 interface, this is not the same inbound nat or portforward for devices on your lan from the internet. Change your outbound nat from auto to manual and post your rules. You will see a nat from your inside network to your opt1 network. With all due respect its not rocket science here ;)
I don't really care how you setup your system - just pointing out that the instructions are correct, if followed correctly ;) You don't set a gateway on a interface that is just talking to that segment, a gateway on an interface is a WAY off that segment.. That is not needed to talk from 192.168.0.5/24 to 192.168.0.1/24 for example