Brilliant!
I removed the 2 NAT rules I added earlier, and added a new rule for the WAN interface, with the source as the /26 network, and selected No NAT. I switched it over to hybrid, and made sure the server was still online and that NAT was disabled for it (using a cURL command to send a request to a public IP return service). My backup LAN device still wasn't able to get out, but I looked down at the automatic rules and noticed that even though they included the LAN network in the source (all interface networks, actually), they were set for only the WAN interface. I created a new rule on the LAN interface with the LAN network as the source, and selected Interface Address for the translation address. Now the LAN device can get out on the main IP and the public routed subnet works fine also.
Thanks, this was helpful.