As the ancient maps used to have inscribed near the edges, "Here be dragons." The confusion of Gadd(e)y and Geddy in the New Kent/James City-Williamsburg-Gloucester area of Virginia unfortunately complicates life for us in Halifax-Edgecombe, for it would appear that both Geddy and Gaddy names co-existed in the latter area, and have not infrequently been changed back and forth to suit the fancy of the transcriber. I have been suspicious of there being a William (s/o William and Mary of VA and brother? of Thomas, Sherwood, and George)who had moved to Halifax prior to Thomas migrating from Bedford to NC in 1760. And that there was already a Geddy (gold, silversmith) in Halifax.
(I have teased about the possession of gold being the distinguishing mark between Gaddy and Geddy.)
Having pursued the McKinnie/McKenne/McKenney tie for some time as a Gaddy relationship, I was taken aback to see in Vol. 2 of William S. Powell's "Dictionary of North Carolina Biography" (UNC Press, 1986) the entry for "Geddy, John (1748-1799), silversmith and patriot...born in Williamsburg, Va., the som of James and Anne Geddy." The article states that John Geddysettled in Halifax in 1768 "at the time of his marriage to Patience McKinnie of Halifax." Patience was the d/o John and Mary McKinnie. The article, which I commend to your attention, establishes what appear to me to be hard and fast McKinney (or however one spells it) ties with Geddy, and not Gaddy.
I realize this doesn't answer your William question. I wish I could: there are points at which the Gaddy puzzle baffles, like a three-dimensional chess game. All we can do is to try to note the possibilities until something emerges. Perhaps your research will provide the key.
As to T2's wife (referring to Thomas, s/o Thomas and Lucie/Lucy from Va to NC 1760), I know of nothing solid on Martha. Millicent/Millison seems valid for the (last?) one; Jane reported as an earlier(?) wife.