I agree with the children as given in 2.1 Children of Thomas Thayer and Hannah, with the exception that Elisabeth was the third child. I have no record of Margery, nor of Mary Thayer Jackson, not in TFA nor in the Braintree records which I went through with a fine tooth comb. I agree that she is an unknown. I would think Margery was most likely my immigrant ancestor's wife [and could be merged], but where does the 1645 birth year originate?
Also, I have no record of Deborah born to Thomas and Hannah as shown on pg 1618 of Sprague. Patricia Muno does not have her included in TFA and I was unable to find her in VRs.
Just an FYI, I do have Mary Neale as John's wife, and that she was sister of Ebenezer's wife, Ruth Jackson Neale.