I also have McFadden ancestors from Raymunterdoney parish. They lived in Derryreel West townland. I looked at the 1901 census for the parish and there were quite a few Harkin families in Ray.
There is a Facebook page devoted to Falcarragh, Crossroads, Gortahork and Gweedore https://www.facebook.com/groups/176041022429045
Have you taken a DNA test? Maybe we can compare if you have taken a test.