When I was looking for the citizenship papers for my Scranton John Manley, I came accross one for a John Manley, who petitioned in Carbondale PA on September 8, 1858. I've attached a jpeg image (unfortunately this board won't let you post a pdf file which would have been a smaller file). Given that your Dunmore John Manley's obit said he came through Carbondale, this might be him. Someone named Martin Lavelle sponsored him. You might want to check the 1860 Carbondale census to see if your John lived there then and if he had a neighbor named Lavelle. These guys often had neighbors sponsor them.
San Diego Peter Manley