The book "History of The Brush Valley Evangelical Lutheran Church, Indiana County PA." by Rev J Milton Snyder is available online as a pdf by typing the title into a search engine. Both the name Bower and Bowers appear often in there. I didn't find anything for George Sr., but George Jr. may be in there, since his sisters, Catherine and Margaret are listed, with their birth dates. That is how I found "my" George Kellar- the birth date matched that of his baptism in York county.

Have you thought about transcribing the letter and posting it here and/or photographing it and posting the photo? I worry about exposing it to too much light too often as that will fade the ink.
In case anyone is interested, William did join the army and survived the war. It sounds like Nicholas may have already been in the army at the time of the letter, and I can't find him after that, so who knows. Perhaps he enlisted in a different state, just to confuse me.
Raona