Eric, you are wandering all over the place again. The way to understand something like this is to focus of a few examples. None the less, I am going to follow your helter-skelter approach just this once.

Re Paul: Scholars currently regard no more than 7 Epistles as "authentic" (1Th, Gal, 1Cor, 2Cor, Rom, Philip, and Philemon). That is, they are letters (their genre) written by St. Paul to the communities named. Most of the others retain the same genre (letters) but were in all probability not written by Paul, but rather by others largely adopting Paul's theology and style. All were written before the Gospels, and all have been accepted and revered from the beginning as solid Catholic doctrine. (To us it is scandalous to impute something to the pen of some famous person that they did not write; in the ancient world this was common, and not scandalous.)

Re: The Psalms are indeed poetry, but a unique Hebrew form of poetry without the rhyme and cadence that we have until recently...