My brain may explode Alan:) The WikiTree site Stewart-30737 is my older sister, who is undoubtedly wondering why I have just asked her to upload her DNA to her own profile (which she has already done). I can only plead that I just got in from a stirring performance of Handel's Messiah.
I also have a profile there Stewart-30742 and of course we share the same family tree on WikiTree as their rule is one profile per person. I was so frustrated with what I considered to be her abysmal referencing (not that mine is much better) that I started my own.
Our William's WikiTree profile is
https://www.wikitree.com/wiki/Stewart-30742. I have just added your information about Janet's possible death on the research notes for Janet.
Not only is there a William Stewart and Isabel Dow in Clunie and Caputh, there is also a William Stewart born 1770 in Auchtergaven, whom I suspect is the father of the Peter Stewart born 1809. Here is another huge mystery. My Gt Gt Gt (?) grandfather William Stewart born 1817 appears to have been born 10 years after the others (discounting Peter in 1809). What a tangle.