In general, your analysis seems very sound.I wish I could give you a definitive answer as to whether you come through "William Sale II" who lived in Halifax and Wilkes Counties, NC and died in Wilkes County in 1788), or some possible brother.Whatever brothers he may have had left hardly any traces anywhere.
A couple of nits:First, I trust you would agree that several of the birth years mentioned (in addition to those where you said "ca") are approximations.It is very helpful to use rough birth years as one tries to sort the generations out, especially in a family like this where the same given names appear over and over, but in my view it's also important to distinguish between estimated birth years and exact ones.Alternatively, if you have a solid source for (for example) the birth year of William son of Cornelius at 1692 exactly, I would be interested in knowing of it.
In that regard, based on the record of the imprisonment of William Sale II during the Revolutionary War, I think it's likely that he was born closer to 1720 rather than 1725.
Other than that, I would like to point out that the proposition that Shell or Schell was the maiden name of Nancy (wife of the William Sale II mentioned above), is, as far as I know, extremely dubious.
Their son Cornelius was old enough to be appear on a tax list in - was it not? - 1772, such that he was probably born no later than 1751.Thus, William and Nancy would have been born by 1750.At this time, William was almost certainly in Virginia, as there's no record of him being in North Carolina that early.I have seen no indication that he was anywhere near anyone named Shell at this time.If I recall correctly, the Shell idea is based on a Moravian record, but to my sense it came way too late to constitute a sure link to our Nancy.If you have any evidence to the contrary, I would love to hear about it.