Have you seen or do you have a copy of the book The Campbells and other Glengarry-Stormont and Harrington Pioneers? There is a lot of info about your Campbells in it, unfortunately not about Peter A. Campbell and Margaret Lothian. I am researching the Lothians, but as yet, don't have this lineage. Most of these Campbells and Lothians lived in Breadalbane.
I found the lineage of John Wilbur Campbell and his wife Emma Christina Campbell. If you have an email address I can photocopy and scan from the book. Sylvia Lothian