Bern,
Thanks so much for that post. After trying some of those steps, like trying to reach the remote subnet from the router, I was able to figure out the problem.
The remote machine with the DNS server has two NICs on different networks. The primary NIC, with the default gateway, is not the network that resolves back to the router. I was already aware of this from previous VPN setups, so I already had a persistent static route for my local subnet here back to pfSense router. This is what made me think it couldn't have been this kind of problem, because clients on this end could contact that machine without a problem.
It wasn't until after I tried to use the local router to connect to that machine that I realized that it couldn't, but it could connect to other machines on the remote end (which used the correct gateway by default). What I needed to do was add a persistent static route on that machine that routed the "internal" subnet of the VPN (172.whatever) back to the gateway, and all is well now.
Most users wouldn't run into this but hopefully this helps someone.
Thanks again!