Are Paul's seven letters authentic?

 Today, the following email reached me:

Dear Markus,

I enjoyed reading your views on Marcion, I found them very interesting and convincing!   My professional interests are in modern history so I have only an amateur's knowledge of New Testament Studies.  Without dismissing it outright, can any strong case be made that some of the authentic letters of Paul are actually not authentic?  I know the Dutch radicals argued against some of them long ago, and some of their arguments are summarized (badly) below.  Are the seven letters considered authentic because of a form of scholarly orthodoxy (like the idea that Marcion came long after the four gospels) or because the evidence is very strong?  

Thanks very much for your time,

Stephen

a)  The letters are treatises not letters especially the very long Romans and First Corinthians

b)  Left no trace on the history of the churches they address

c)  Catholicizing terms are used 

d) Internal contradictions and discontinuities 

e) Confusion over Paul's relationship to the churches he is writing

f) Complexity and depth of the theology and ethics anachronistic for 50s CE

g) Pronounced post-Jewish Christianity of the letters could not have emerged so soon after the death of Jesus

h) Concerns addressed in the letters are anachronistic for the first century

I) Rejection of Israel in Romans 9-11 suggests period after the fall of Jerusalem

j) Persecutions mentioned in the letters were anachronistic for the 50s CE 

to which I replied:

thanks for asking this crucial question which bothered me for some years and to which I have not yet formed my opinion. However, as I write, I am working on a parallel monograph to the one by which Matthias Klinghardt reconstructed Marcion's Gospel. So far, I have gone through Galatians and 1 Corinthians up to chapter 10, if you read Greek or German, I am happy to send you the draft to that point.

But what I discovered - something that astonished myself is the following observation.

Based on our witnesses (Tertullian, Epiphanius ...) and on papyri and manuscript variations in the tradition of the Epistles, it is clear that they attest to two very different collections of Paul's letters. More on this I am publishing in the nearer future with a book by CUP, but which I am now detailing in the current study.

Marcion's collection had the known 10 Pauline letters, of which 7 are commonly regarded as authentic (except for some critiques like the Dutch radicals). There argument are heavy, though.

The question then is - what is the nature of the letters in this collection. As far as I can say today, one notices in the semantics some differences between the Pseudo-Paulines (2 Thess, Col, Laod) and the other seven letters. However, all of the 10 letters reflect such a proximity to the semantics of Marcion's Gospel, as reconstructed by Klinghardt that it looks as if we have only a few options on the one result from my initial study of Galatians and 1 Cor 1-9: the person who has written or thoroughly revised the Gospel is the same who has written or thoroughly revised the letters.

1. This person is Paul
2. This person is a student of Paul, Luke
3. This person is a later anonymous redactor
4. This person is Marcion

But more we will know when I have finished the exercise of comparing in detail the reconstructed form of Marcion's collection with that of the canonical revision.