You have been really busy! I've spent the afternoon checking the info that you've sent and it looks like you are right on! I had David Polk Mattox in my database, but didn't have a spouse for him.
I found a Warren M. Ellis, married to Julia A. Kemp, parents were James Kemp & Sarah (no maiden name); but no Warren Preston Ellis. I did find that "Polk" in David Mattox's name was a nickname; that his real middle name was "Preston." I found a picture of the headstone of Warren Ellis and it has "M". You can find it on Find-A-Grave in Franklin County, VA. The "M" could be an error; it happens so many times when the wrong info is given to the person doing the headstone.
Also, Zachariah Ellis' wife, Malinda (Linda) Dehaven, was a sister to Abraham Dehaven, the person who originally left the Bolling children as heirs to his estate; thus, part of the suit that Wesley Mattox brought again Zachariah Ellis, that included the Bolling children.
Abraham Dehaven, Sr. was married to Rebecca Pawling and lived in Loudoun County, VA. In his will, Abraham,Jr., and Isaac Dehaven (twins) were named executors of his estate. Isaac Dehaven was married to Elizabeth Ann (Nancy) Ellis; two of their sisters - Sarah Dehaven was married to Robert Ellis, Jr., and Rebecca Dehaven was married to Elias Ellis.
Now, on to the Joseph Bolling-Rebecca Maddox/Mattox info:
Three of their daughters, Nancy A., Margaret (Peggy),Sarah Peggy (Sally) were all married to 3 Cook brothers.
Two of Rebecca Maddox's sisters, Margaret (Peggy) Maddox & Sarah Prudence (Sally) were married to Kemp brothers, Jordon Kemp & Robert Kemp. So all of the families are connected FOR SURE! So more research to do! I'll send you by separate email a more detailed info sheet.
Thanks for all your research - I'll continue to pursue our connections.