I (finally) started an OpenVPN server and configured my home network for VPN and IP Passthrough. Testing with my laptop, I got confirmation of a successful connection but for all my testing it appeared dead. No internet, no network visible. I had to revert network configuration before leaving for work this evening due to an as yet unexplained loss of connectivity on other network devices. After enabling remote administration, I was able to make another attempt during downtime at work however my employer appears to be blocking VPN. Port 1194 is a common port registered to OpenVPN so after running netstat -b I found an active TCP port used by chrome and since they apparently weren't blocking that port, I edited the OpenVPN configuration to connect to that port on my remote network, then configured port forwarding so that any incoming requests on that port were sent to the VPN server's address and port.
Having talked myself through this just now, I wonder if, instead of pointing requests on that port number to the server-assigned IP, I should have pointed those requests back to the gateway's internal 192.168.1.1 IP and let the firmware handle the request from there as I had told DD-WRT the required information for the OpenVPN server.