My two cents for what it is worth:
As far as placement goes, I would go with placing it in at least the same cemetery as his
wife was buried in. Knowing where he fell, yes, learn that if you can and all the information
that you can.
As many men as were killed during the war, if all had a marker setting out somewhere,
the countryside would be covered over in many Southern locations.
I had at least two relatives at Shiloh, and no one has a clue as to which burial pit they were
thrown into. I had an uncle taken at Helena and he was till alive when the war ended in
one of those hospitals that took care of so many, but he never made it home.
I am fairly sure that my ggg grandfather is buried as a CSA unknown on the outside of the
National Cemetery in Little Rock.
So I do understand the desire.