1. The 1903 book's paragraph on "McDowell or McDole" (page 976) concludes with "In 1784 Thomas and William went on to Shirley Hill, Goffstown, where they parted, Thomas going to Vermont where he was never heard from after." If this 1784 date is correct it seems a cinch that the three generations from original emigre to one of his sons to adulthood to marriage and family could NOT be sufficient to cover the years from "1630 or 1640" to "in 1784"!
2. Also, with some three hours of reading and checking I have located on page 315 of "The History of Bedford" the following - which I had read several times before but had not connected the conflicting aspects of the statement: "John McLaughlin and Mary, his wife, came from Ireland about 1735;" - obviously not close enough in date to support the trail of events from the genealogy on page 976.
A better way would be to have gone to Google and found the book. It is
and download the text version (the PDFs don't seem to be searchable) and look for your names of interest.
3. Interestingly, I personally located the graves of William McDole "died 1784, at 65th year" therefore born 1719 and of Rosannah McDole "died 1791, 64th year" therefore born 1721. A single 2" slab - wide enough to stretch across both graves - in Hillside Cemetery (Grasmere, NH).
4. Do you ascribe to what I've been told: That those two-graves-wide headstones use the wife's name BEFORE marriage? If so, "Rosannah McDole" on her stone verifies her prior marriage to William's elder brother, Thomas . . . when the two McDole's, the wife of one and children of two of them arrived in Bedford, Rosannah was then the wife of Thomas and mother of his several children.
To ascribe to it would mean that I considered such rule of thumb to always be true. I don't believe that anything is always true. This tombstone exists in isolation and given that the last names match it does not mean much. You will need to find other evidence to support the possibility of the prior marriage..