"However Nememiah son of Samuel has a son Samuel who dies around 1750 at the age of 27....which would put his birth around 1722...his grave is in Boxford MA."
I am not sure what this Samuels death has to do with any other Samuels. I believe that Samuel Porter who was married to Sarah did not die until 1779. That being the case he was definitely alive in 1766 to father Samuel who later married Persis. I have not looked at the primary sources myself though as this is not my line and I am related to the Porter family solely through marriage.
I can not recall where I got the information from but what I have seems to say that Samuel(1722) was born in Salem, Ma and later bought property in Lebanon, CT in 1750 which he sold in 1778 after having moved to Hartford, VT in 1774.