As you know Clonegal is a border parish meaning the parish covers area in two or more counties for Clonegal, three counties.
Most marriages occurred in the bride's parish and likely the parish where the marriage occurred no longer has records back to the 1840s. For example, the nearby parish of Kilrush in Co. Wexford does not have any marriage records on the NLI site which possibly means those records are not available. https://registers.nli.ie/parishes/0569
Moylisha sounds like Melitia and since you found Nolans and Halpins in the townland, likely you have the correct area.
With out more evidence, I would be hesitant to use that 1815 reocrd. Too many John and Patrick Nolans.
Have you tested your DNA?