As John McDonnell (or M'Donnell - watch for variations!) is variously a gentleman farmer, and ship owner, he should have substantial property, and one would expect his father to have had too.
Two addresses are mentioned: Gruig and Cushendall.
This suggests to me searching in Griffith's Valuation for John and/or his father. GV for Antrim was published in 1861.
e.g. in Gruig I see two McDonnells, Randal and Daniel - but neither has a house, and only small plots of land. Multiple McDonnells in Cushendall. Elsewhere in civil parish of Layd I see McDonnell and O'Neills sharing ownership of over 1,000 acres.