After the 1852 directory entry showing him at High Street in Carrickfergus, subsequent directories for 1858, 1863, 1865, and 1870 on the PRONI street directory website (also 1868 on the Lennon Wylie website) show him in Larne, but with no address specified. None of the street directories mention Isabella.
However, Griffith's Valuation (with a local print date of 1861) shows William as a lessee in Dunluce Street in Larne. The Valuation Revision Book for Larne (1863-1866) shows him still in Dunluce Street, however his name was then crossed out and elsewhere in the Book written over the top of someone else in Pound Road Larne (Pound Street today), effectively showing him moving there (precise year isn't shown). The Valuation Revision Book for Larne (1867-1878) shows him still in Pound Road, however his name was then crossed out.
Besides living in Carrickfergus and Larne, I can see no evidence of him living anywhere near St. John's church. He could have hitched a ride on a boat from Larne to the likes of Ferris Bay or had some other similar arrangement across Larne Lough, say, from Magheramorne, but I don't see that as terribly practicable and since we know that a horse and saddle were among his effects sold off after his death, I imagine he travelled to and from the church by horse. With the church being just short of halfway up the Islandmagee peninsular, and Carrickfergus and Larne being about 9-11 miles from the church, I'm guessing it took from 1 - 1 1/2 hours to ride there.
There is evidence in 1850s newspapers that his involvement in "politics" in Carrickfergus raised some hackles on the basis that he was deemed an outsider.