Without going in detail, Kosta, my opinion is that there is nothing in St. Paul's writing that in any way separates him from the other Apostles's writing.
Two groups try to separate him. One is a certain marginal nondenominational movement that looks for "authentic" or "historical" Jesus, and they sometime see in Paul somewhat of an impostor, someone who created organized or judaized religion out of a simple non-dogmatic ethical teaching, best described in the book of Matthew. The less we say of them the better.
The other is some currents of thought in serious Evengelical Christianity. They correctly see in St. Paul a different, more systematic and more theological kind of writer, someone who is convenient for their prooftexting. I have seen, for example, the view expressed (not by any of the posters here, although Blue Duncan seems to come close at times) that the parables of the gospels are something that was not addressed to us, and that the Epistles of St. Paul alone are sufficient to understand Christianity. If you look at St. Paul through such Protestant prism you will begin to separate St. Paul from the rest of the scripture. This is what your post reminds me of.
But I refuse the prism. St. Paul is different because his background is different. However, he teaches the same Orthodox Christianity as anyone else in the Church. In particuler, the notion that he somehow teaches the gospel of faith alone in contradiction to St. James is a myth. I once had a dispute with someone who was doing the familar couple-dosen quotes for Romans to prooftext for me that salvation is by faith alone. All I had to do was ask to read the same letter to Romans to the end. The myth was demolished by St. Paul himself.
I think you are touching on the (some) protestant doctrine of Dispensationalism.