Unfortunately, the RC parish of Dunfanaghy does not have records until 1877 so no church marriage records are available in that church prior to 1864. In 1864, civil registration of RC marriages began although initally not all marriages were registered.
Here is the 1864 marriage record for Grace Strain to Manus McFadden.
Civil death records also started in 1864 but I did not find a death record for Hugh Strain. Possibly his death was not registered.
I have McFadden ancestors from the next parish to Clondahorky (Raymunterdoney). Have you tested your DNA?