All the evidence that I'm aware of shows Benjamin Isbell, his wife being Lettice Hickman, is the son of William Isbell and his wife Rosamund. Not Henry. Benjamin had a brother, Jason, not William. And I am not aware of Jason's descendants.
As for not being able to take the Isbell DNA test because your female? This is nonsense. The Isbell daughters CAN take an Isbell family DNA test. While not a direct line test that the male takes, it can be used to identify cousins, aunts and uncles between the male and female lines and you can go back five generations.Is your father alive to take the DNA test?? Regardless there IS a test that female relatives of Isbell males can take. Got to the Family Tree DNA site, FTDNA, and check it out.