Happy to help.
For the benefit of other readers - if an interface has a gateway set, then pfSense by default assumes it is a WAN-style interface, a pathway to the public internet, so things like automatic outbound NAT are done on those interfaces to translate LAN IPs into WAN IPs suitable for the public internet.
If you have a LAN like this OPT1 that is just a local subnet with a gateway to other internal networks, then you do not have to set that internal gateway as the actual gateway on the interface settings. You can just add a gateway in System->Routing and then add static route/s telling pfSense what internal networks are reached through that gateway. Then pfSense will understand that it is not a gateway out to the public internet in general.