My name is Julia Totty.  I was looking at the information you posted on the Davis family on ancestry.com.  My 3G Grandparents were James Madison Davis and Sarah Emmaline Bills.  Their son, Anderson Harvey Davis, my 2G Grandfather, married Katie Tennessee Edwards in Saline/Grant County Arkansas.  You may know most of the Davis family moved to Arkansas from Tippah County sometime after the civil war.  
 
I think you are correct about Sarah Bills father being John Bills.  I'm looking at John Denman Bills, youngest son of Daniel and Deborah Denman Bills, but have not been able to confirm.  My grandmother wrote on the back of an envelop that Sarah Bills' father was a senator from Mississippi, but I don't know if that is correct; still checking.  Also on that envelop was the name John Davis, perhaps as the father of James Madison Davis, so I think you are the right track their as well.
 
In a letter written to my grandmother in 1964, her cousin stated that our Davis genealogy information was in a box at the home of a son of Liza Corley (then in her 90's).  Do you have any contact with the Corley family?  Another letter from my uncle to my great grandmother, Stella Modena Davis Eakles, states that her grandfather, James Madison Davis, was in the Civil War and fought in the battle on Lookout Mountain.  He was imprisioned at Rock Island Prision during the war.  I'm also persuing that as well.
 
As you may know, the Bills family is well documented, but I have not been able to verify Sarah Bills is the daughter of John Bills.  If she is, did you know that we are related to Prince William and Prince Harry of Windsor?  Their mother Diana Spencer is a descendant of Catherine Bills, daughter of Nathaniel Bills, and brother of Gersham Bills born in 1711, Daniel Bills' father.  See http://us.geocities.com/Heartland/Hills/1150/hww.html. That makes Prince William and Prince Harry my 8th cousins.
  
I don't have my genealogy information from my old computer, but will be happy to share information when I get it transferred if you are interested.