Perhaps it's more blasphemous to credit false prophets?  

"To deny the existence of Paul, to attempt to relativise his message, to reduce the historical resurrection to mere myth, to assert your own feelings in the matter contrary to sound doctrine and historical fact, are all indications of such --Blasphemy--"

The Bible is not a historical text. It contains a message.

Perhaps it's more blasphemous to credit false prophets?

None, zero, nada of thse scriptures were written by your attributed authors. All were written at least a hundred years after their deaths. There is also some critical thought that the same author wrote all four and again: a hundred+ years after their death.

your concept of God is derived from what authoritative source exactly?

What "authoritative source" proves the existence of God? None. Zero. Nada. Because faith isn't faith if it's based on evidence. At that point it is a science.

Do you believe in a "soul" that survives the death of body?

The proposition I presented your narrow mind was Don't even go to the 'souls' thing because there is no evidence outside of certain religions that ensoulment is unique to humans. No denial of the soul in that.

For that matter, if sin is a human based culture thingy  What is there for God to "forgive" among humans?

Only God knows. Me, I'm gonna err on the side of caution and attempt to do right in every thought or deed. That's respect enough unless you're a pharisee.

The fact of the matter is I doubt all dogmatic religions. That's why I prefer the Society of Friends- Each of us has direct contact with God and each of us has to decide how to do right.

P.S. Your dog does not, can not commit a sin. He can have no consciously immoral intentions, a prerequisite for culpable wrongs.