GruensFroeschli,
Thanks so much for the advice – I've added this routing to both pfSenses and the gateway, and it now appears to work! It still didn't cooperate until I remembered I had the firewall enabled on a linux box that was hosting the pfSense server on a VM -- needed to allow the remote network rather than just the LAN and WAN IP addresses of the pfSense box. But the real sticking point was the routing, thanks again for your help.
-Ned