I'm sorry I can't verify the parentage of Mercy Jipson except to say that I have a small book about the Jipson (Jepson, Jephson families) family. In it at the beginning is a statement, "The Boston records state that one of the lineal decendants of John Jepson, (who came to Boston in 1647), John, and his wife Mercy, had a son, Michael, (born) August 21, 1716." Further it says, "Micah Jepson of Hingham must have been born at about the same time, also since the Jepson family of Massachusetts was quite a small one, I am confident that the name Michael in the records is a mistake and should be Micah. This opinion is strengthened by the fact that Micah Jepson named two of his children John and Mercy, the names of the parents of Michael Jepson of the Boston records."
I have other information on the family "after" this time but not before. Possibly you could trace going the other way? Quite of few from this family are buried in the Goshen MA cemetery. Good luck!