I am +90% positive that it is my relative. My grandmother is on the very same headstone (it is a large memorial), and my mother confirmed the location... so it is about as sure as it gets, I think.
I am actually not as positive of his spouse's maiden name. She is listed on the headstone with the same surname, so that complicates things a bit.
I did find purchase records of the plot online. Again, same surname, but the man does not appear in my tree anywhere. So, a relation (perhaps), but I don't know what.
I don't think there was a trade organization. Census records list him as a "farmer" from the 1850's to the 1880's.
...but I know there is a county historical society, and I found the church on the internet. Time to fire off a couple of emails.
Thanks for the advice.