Pseudonymity in the New Testament?

As I'm working my way through the Pastoral Epistles, the question of Pauline authorship naturally comes up.  The general consensus among modern day New Testament scholars is that these letters were not written by Paul, or possibly that some genuine Pauline fragments were later expanded and used in order to combat heresy in the Ephesian church.  Advocates of this view give the following reasons:

1. The cities and events recorded in the Pastoral Epistles do not fit into Paul's three missionary journeys as recorded in Acts
2. The vocabulary and grammatical structure of the Greek (ie. omission of article) are so different from Paul's other "genuine" epistles that they could not possibly have been written by the same person
3. The ecclesiastical situation described in the Pastorals reflects a second century setting
4. The heresy Paul is combatting in these letters is Gnosticism (which didn't emerge until the 2nd century)

 Furthermore, high profile and moderately conservative New Testament scholars such as Bruce Metzger claim that Pseudonymous writings were a legitimate genre during the first century that would have been accepted without question.  Since the original readers didn't share our modern standards of plagiarism, it is anachronistic, they say, for us to view these books as forgeries.  Instead of getting too worked up about the importance of apostolic authorship we should listen, rather, for the authentic apostolic "voice" regardless of who wrote them.

This sounds well and good, but what is really at stake here??  In my own view, quite a lot!  For starters the primary teaching regarding the inspiration of Scripture is found in 2 Peter and 1 Timothy.  If we reject apostolic authorship of these books, we bring into serious question the authority of Scripture and the Evangelical doctrine of the infallibility of Scripture.  Secondly, these books claim apostolic authority and contain statements of eyewitness testimony.  The author of 2 Peter states, for example: "For we did not follow cleverly devised myths when we made known to you the power and coming of our Lord Jesus Christ, but we were eyewitnesses of his majesty....we ourselves heard this very voice from heaven, for we were with him on the holy mountain."  It stretches the limits of credulity to think that first century readers could have accepted a statement like this as authoritative  if it was not written by Peter himself who was an eyewitness to the Transfiguration.  Secondly, most of the New Testament instruction regarding church order and structure are contained in these books (ie. qualifications for elders and deacons).  If these are not genuine apostolic instructions, then it seems that we Protestants are more dependent on the traditions of the early church than we'd like to admit.  Thirdly, this theory brings into question the legitimacy of the canon of Scripture, since apostolic origin was one of the primary criteria taken into consideration when the canon was being formed.  If 2 Peter was initially accepted into the canon because of its Petrine authorship, it raises the question whether it should still be considered part of the canon now that we 'know better'.  It also raises the question of whether the church should reconsider other pseudonymous writings that were rejected as spurious.

In response to the objections listed above, I offer the following responses:

1. The Pastoral Epistles don't fit into the chronology of Acts because Paul was eventually released from prison in Rome and went on a fourth missionary journey to the Western extreme of the Empire (probably Spain).  He was later arrested and condemned to death under Nero. Clement's own writings seem to confirm this hypothesis since he speaks of Paul taking the gospel to the Western extremities of the Roman Empire.
2. The objection based on vocabulary and grammar is a classic example of begging the question, where the conclusion of an argument is assumed in the premise.  Liberal minded scholars exclude the Pastorals a priori then proceed to argue that these  epistles don't contain "Pauline" language.  Its much more likely that Paul, an well educated man, had a much wider vocabulary than we give him credit for.  Also, the pastorals deal with different subject matter than the earlier epistles and so we would naturally expect him to use different vocabulary.
3. If we accept the hypothesis that the Pastoral Epistles were written at the end of Paul's ministry (based on external testimony from the early church), there is little reason to conclude that ecclesiastical structure couldn't have progressed to reflect the situation described in Timothy and Titus.
4. It is impossible to say for sure that the heresy Paul was combating was full blown Gnosticism.  There were certainly first century precursors to gnosticism.  New Testament scholars still have not reached a consensus as to the nature of the Colossian heresy so perhaps we should reserve our judgment here in the Pastorals too!
5. The internal evidence of the New Testament call into question the common theory regarding the acceptability of pseudonymous writings for Christians in the first two centuries (cf. 1 Thes 2:2).  Paul sometimes signs his letters with a special mark to ensure their authenticity and to defend against forgery.  I personally have a hard time believing that he would have approved of a well meaning disciple putting words in his mouth long after his death.
6. It seems a bit presumptuous to claim that we know more in the 21st century about what is and is not Pauline than the early Church Fathers who accepted the Pastorals as authentic.  The only person that I know of who rejected  their authority was the notorious heretic Marcion, who also rejected the Gospels and the Old Testament.