I am also a descendant of John M and Nancy J.
We just got back from a reunion at Seymour, MO where there were Buff's and Lee's. John and Nancy's son Harvey had a daughter Riter Elizabeth who married Isaac Henry Lee and had my grandfather Martin Alexander Lee.
The only Buff's we knew were in OK besides us was Elijah Buff's gr grandkids. They grew up in Beggs where my mom is from. Would be absolutely delighted to share info!!! :o)