I suggest that you concentrate on who Henry Seabrook was. There is a William Seabrook recorded as a Road Contractor. He had brought proceedings against some men at the the local magistrate court in Newtown Barry - now named Bunclody - in 1838 for damaging the road.
Griffith's land valuation c1850 has just 10 of that surname and they are in Carlow, Wexford and Wicklow. There is no "Henry Seabrook" that I can find in that area. William Seabrook in the parish of Agha, Co. Carlow has a House, Offices and c211 acres of land there.
There is a record of a William H. Seabrook in the police in 1816 who was born in Co. Wicklow.
The surname "James" is fairly widespread and they are recorded as Protestant and Roman Catholic.
Have you tried to make contact with descendants of the Witnesses at the marriage.