I have not seen Arvord's work, and I don't know how much work ya'll have done here, except that Brian, who went to school with my husband, is STUCK! I threw out that tidbit because my database clearly says that Miles and Ursula were of an age to be either the parents or grandparents of the Michael (Miles) Abernathy who married Isobel West and I had that note about them having two daughters and one son. It might be unusual, but not impossible, for a child to be born 15-20 years after the wedding... Since he was reportedly still alive until 1812, what do the census records for 1790, 1800 and 1810 have for Miles? What county can he be found in on those census years??
One of my direct ancestors married for the first time in his life at the age of 45 and then had two boys and a girl, which he lived long enough to see the one surviving child married.
Someone else suggested that if you're having trouble climbing up the tree, try climbing down it. In other words, instead of trying to prove that Miles and Ursula ARE the parents of Michael, try proving that they CANNOT be Michael's parents.
As my granny would say... There's more'n one way to kill a cat than chokin' it to death on butter...
Good luck and keep us appraised of any new developments.