Welcome to Ireland Reaching Out!
I also have a McFadden great-grandmother who emigrated to Philadelphia around 1868 and she came from Raymunterdoney parish in Co. Donegal. I see that you have posted in five parishes in different parts of the county. We do have a parish liaison in Clondavaddog parish and I will send him an e-mail alerting him to your message.
It is very difficult to research ancestors from Donegal who were born in the first part of the 19th century because very few church records are available prior to 1850.
You may want to consider autosomal DNA testing to see if you match up with someone who has more info on your McFadden line. My autosomal DNA test helped me pinpoint the exact townland where my great-grandmother was born. There is no guarantee that your matches will provide you with a similar outcome.
FYI. I have a sister who lives in West Chester.