Patrick,
In terms of discussing these issues with your co-worker, whether or not you find secular text critics or historians who might agree with the traditional attributions of NT authorship, it seems you are conceding to him the superiority – or at least equality – of secular scholars in this matter of discerning NT authorship. If you have to do that so you “might be able to get his attention at least enough to get him to listen a little more” it seems you are compromising your solid position of evidences just to get a hearing from him, this one who boasts “he annihilates most Christians or at least causes them to give up pretty quickly”.
Could it be that his cordiality and good humor in this “conversation” with you is but the high-spiritedness of the confident attacker and destroyer of the Christian faith? Be clear that he is an enemy of God and the Gospel of Jesus Christ, a mocker of sin, judgment, and the costly atonement procured by the Lamb. By his arguments he seeks to annul the dictums of the word of God as regards his life and impending eternal death. This “sport” of his is no game to him – though he may laugh and smile (“one gets more flies with honey than with vinegar”) – but an earnest seeking to “annihilate” the faith God has gifted you with.
I would not primarily seek to convert him to your views, but rather to adequately defend the Biblical truths, and your own faith in them. While the topics he brings up – these historical / textual matters (CharlieJ is right that your present contention with him regards historical criticism) – are pertinent issues, remember that your co-worker is seeking to fend off being accountable to God, and his desire to “annihilate” your faith in God’s word is how he fortifies himself in his sin, i.e., constructing a “high thing that exalteth itself against the knowledge of God” (2 Cor 10:5).
Here are some examples of current Christian scholarship vis-à-vis the methodological scepticism of Ehrman and the like:
Dr. Richard Bauckham (10 minute Youtube clip),
Jesus And The Eyewitnesses: The Gospels as Eyewitness Testimony
Dr. Richard Bauckham (1 hour, 10 minute Youtube clip),
The Gospels as Historical Biography
Dr. Peter Williams (1 hour, 2 minute Vimeo clip), New Evidence the Gospels were Based on Eyewitness Accounts
Dr. Peter Williams, Analysis of Bart Ehrman:
Misquoting Jesus and Evangelical Textual Criticism
When your co-worker sees that you are neither demolished nor ready to give up, but are able to support / substantiate your defense of the traditional attributions of NT authorship, perhaps he will cool his jets.
Jesus often did not answer His opponents on their own terms – i.e., according to the premises of their arguments – but on
His terms, which were spiritual, solid, and irrefutable. You will not be irrefutable as Jesus was, but you certainly may produce spiritual, historical, and solid evidences.