Hi, Jean. Thanks for getting back to me.
Unfortunately I have only snippets on any of these, mostly from the IGI and old notes from my searches of the OPRs years ago. I have no solid death dates for any of these people but since I wrote the query a couple days ago I've discovered some indications that several may not have remained in Benholm. Here's what I have:
Walter Loch and Margaret Fullerton were married Jan 1808 and apparently had children born in Benholm as late as 1827. I am not certain which Margaret this was since at least two in the family would have been an appropriate age. One of those, by the way, is the Margaret Fullerton who married John Law in 1828 and whose stone you've already found - its possible that Loch was the first marriage and after his death she married Law (she was 50 and he was 65 at their marriage.)
John Craigie and Margaret Fullerton were married Nov 1854 in Benholm. Two cousins are possibles for this Margaret, the daughters of Robert and of his brother John who were sons of David, the tenant at Knox of Benholm. Because Robert is found in Lawrencekirk and Garvock at other times, its most likely John's daughter, b. 1828.
John Duthie and Annabella Bisset Fullerton were married Dec 1854 and had a son John in 1858 in Benholm. No further info available yet.
John Greigson and Ann Fullerton (b.1824) were married June 1845 and had three children in Benholm by 1850. Ann was another daughter of John, son of David. No more info yet.
Alexander Strachan and Jean Fullerton were earlier - Jean, b. 1745, was the daughter of George and Margaret (Pirie) Fullerton, and sister of David. The marriage is recorded as 1771 in Benholm. I have no information on them other than the reference on the stone for her parents that says she died before 1801 (as did two of her brothers.)
Thanks for anything you find - I've really only just started looking for these families so anything would be new and useful to me.