First off, let me change my subject line for this post to "NAT port forwarding stupidity from no common sense BOOB".
Cry Havok patiently asked me what the default gateway was for 192.168.XX.10.
The answer? THE WRONG ONE. It was set for 192.168.XX.1!!! Upon changing it to 192.168.XX.2 (the LAN for my pfsense box), everything worked just like it's supposed to.
I should be embarrassed (and I am). ::)
Thanks to all who replied, especially Cry Havok, who helped me trip over the obvious! It's always the little things…