I wish I could answer all of your questions on this posting, but I think it would be best to deal with them a few at a time and when it is not so late in the day.
As for Martha Jane Roberts' birthdate...I have her born in 1853.The error could have been on either side.I noticed that the date shown on the Bible page you e-mailed is blurred over with what is an apparent streak of ink, so it is hard to tell....and on headstones, 1853 could easily be mistaken for 1858 and the other way around.
On the James Buchanan listed on the Bible page...there was a James Buchanan Tarter who married a Margaret Trimble.
I think Patrick Green Roberts was another son of Elizabeth and Absolem Roberts, but am not positive.
I have been trying to sort thru the Darter-Tarter family and those which connect to them...the Burton, Combest, Dalton-Daulton, Epperson, Fleming, Floyd, Norfleet, Rainwater, Repass, Schoolcraft, Trimble and Weddle families.
I am a part of the family who kept the Darter spelling of the name.
BTW.. Absolem had a brother, James, who married Eliza Tarter, daughter of John Tarter and Elizabeth Moore.Then there was Isaac Roberts who married Elizabeth Norfleet and Elizabeth Rainwater and Nancy Roberts who married a William Tarter and Jane Mamie Roberts who married Ephraim Littleton Tarter.