Op (I, that is) didn't take this OpenVPN FAQ seriously enough:
One of the most common problems in setting up OpenVPN is that the two OpenVPN daemons on either side of the connection are unable to establish a TCP or UDP connection with each other.
This is almost [always] a result of:
…
A software firewall running on the OpenVPN server machine itself is filtering incoming connections on port 1194 [here 5000-5007]. Be aware that many OSes will block incoming connections by default, unless configured otherwise.
There's no problem with OpenVPN.
I just neglected to create a firewall rule for WAN in the pfSense VM that's running the OpenVPN servers, to provide access for the hidden-service proxy in the Tor-gateway pfSense VM.
How embarrassing. But this question should remain, I think, in case others make the same dumb mistake that I did.