I think you are on the right track. You just need to find the proof. And certainly I agree, there are enough coincidences to warrent concentrating your search in that area.
Did you see my trail of messages added onto my last post? Do you know the names of the children for Paul Lewis and Miriam Fernald? There may be clues in their names.
The division of the property after the death of Miriam (Lewis) Fernald (possible mother of your Miriam), certainly could explain why the estate was divided up by that date rather than directly from the will!! I would look at that document carefully for any clues!
If John died in 1773, he hopefully left a will that's hiding somewhere in the states archives, or perhaps the will of his wife Miriam. (Did widows even leave wills?) And also there are the deeds.
If he is the correct John. You have a whole line of John's to Renald, starting with the possible brother of Miriam!!
6. John Fernald and Martha Jones 5. John Fernald and Meriam Lewis 4. John Fernald and Dorothy Main 3. John Fernald and Sarah Hincks 2. John Fernald and Mary Spinney 1. Renald/ Reginald Fernald and Joanna Warburton