Brian,
I think the townland where David Gaston farmed was Killycreen (which is sometimes referred to as Kilcreen). I see him listed in Griffiths Valuation for 1862 on plot 12a which was a house, offices (ie outbuildings) corn mill, kiln and a total of over 44 acres of land. Nearby on plot 11b was an Alexander Gaston who had a house and garden and is likely to be related. That farm today looks to be off the Killagan Rd, a mile or so north of Killymurris Presbyterian church.
A Martha Gaston was also farming on plot 19. Again she may be a relation, although Gaston is a very common name in the area. (Huegenot origins, I believe).
http://www.askaboutireland.ie/griffith-valuation/index.xml?action=nameSearch
The revaluation records show the farm remaining in David Gaston’s name till 1879 when it changes to Hill Gaston. Then in 1883 to Alexander Luke. Then in 1884 to Robert Gaston, whose name remains there till 1929 when that series of records finishes. The property was rented.
https://www.nidirect.gov.uk/services/searching-valuation-revision-books
2 Gaston households in Killycreen in the 1901 census:
http://www.census.nationalarchives.ie/pages/1901/Antrim/Glenbuck/Killyc…
http://www.census.nationalarchives.ie/pages/1901/Antrim/Glenbuck/Killyc…
1911:
http://www.census.nationalarchives.ie/pages/1911/Antrim/Glenbuck/Killycreen/120371/
William James Gaston married Sarah Caldwell 8.7.1896. His father’s name was Robert Gaston.
I also see Robert McWilliams in Anticur on plot 21a which was a 28 acre farm. It changed to Samuel McWilliams in 1869. You can use the books to trace that property forward.
I found these probate abstracts on the PRONI wills site:
Administration of the Estate of Robert Gaston late of Kilcreen County Antrim Retired Farmer who died 9 January 1900 granted at Belfast to Margaret Jane Adams Married Woman.
Probate of the Will of Matty Ann Gaston late of Kilcreen County Antrim Widow who died 18 October 1908 granted at Belfast to Thomas Gregg and Thomas Linton Farmers. (This will is on-line, and is for Robert Gaston’s widow, the mother of William James who married Sarah Caldwell).
Administration of the Estate of David Gaston late of Kilcreen County Antrim Farmer who died 22 January 1911 at Shell Hill Coleraine County Londonderry granted at Belfast to Martha Gaston the Widow.
Gravestone inscription in Killymurris 1st Pres churchyard:
Erected by David Gaston of Kilcreen. In memory of his beloved wife Jane who departed this life 7th June 1872 aged 40 years. Also of his brother John.
4 Gaston households in Killycreen in the tithe applotment records for 1834:
http://www.irishgenealogyhub.com/antrim/tithe-applotments/rasharkin-par…