Hi Tunji
Yes I see the possibility now of David Walton not being the father of William. The fact that Walter's wife Janet Bett would seem to be have been born around 1714 (her parents Robert Bett and Margaret Dott having married in Leuchars that year. It would bring her nearer to the age of the Walter born in 1712 to James Walton and Margaret Ross!
I'll e-mail you.
Jen