Never too late to reply to a posting! I've done the same after finding messages I missed from years earlier.
I can't dispute your theory of Alexander Davis being the father of Sarah Carpenter Davis and her sister Martha Davis because I have not researched that line for lack of time and focusing on other family lines. All I can reply is that when my great-great grandmother, Margaret Matilda Fore, whose mother was Sarah Carpenter Davis, was asked who her grandmother was, she answered Lucrease Cook, called Creasie, and when asked who her grandfather was, answered Elnathan Davis. I can only tell you what her answers were, and in 1930 when the questions were put to her, she was only 59, certainly not too old to remember, and Margaret was sharp as a tack until shortly before she died at 91. I just can't imagine she would not know who her own grandparents were. I'll be interested to know if you find anything further. Are we kin in some way?