According to Freereg, lots of Buckley's born in Saddleworth, however only 4 Benjamin/Ben baptised between 1790 and 1800 and one of those, a twin died. I noticed your ancestor always uses the name Ben, rather than Benjamin and the only one baptised as Ben is the one that you thought was the most likely candidate, son of James and Ann.
My grandfather was always known as Tom and we assumed his name was Thomas, but he'd actually been christened Tom.
Another thing to suggest is that Joseph Buckley was some relative but not necessarily a brother or father. As I mentioned, Buckley was a very common name.
And lastly, I noticed his son was called Jerry. I wonder where that name came from. Is there a Jeremiah in the family anywhere?
Just a few random thoughts
Chris