This seems reasonable to me. See the post by cyningdun. The most reasonable suggestion to me on the origins of Peter A. Campbell that I have seen to date. Point out to me where this post is incorrect. Do you have a better suggestion? Peter A. Campbell was the father of my grandfather, John Wilbur Campbell. We know that Peter came from "away". Of that I am certain.
Have you looked at "The Campbells and other Glengarry-Stormont and Harrington Pioneers" by R.B.Campbell, 1983 Lomor Printers Ottawa, Canada?