The claim that the Psalms are just poetry is going to be heartbreaking to anyone that cites them as prophecies about Jesus. There are, what, 25 different ones that people use that way? It's the number one source of old testament retroactive bias confirmation that JC is the Messiah. Take away their predictive qualities by making them just prayers said by people and you destroy the best resources for people to justify their core beliefs.
In your attempt to back up one claim you have destroyed 25 others and the bulk of the reason for the new testament. That was not a good move.