For starters I would like to recommend a site called bible.org. It has a series of articles by New Testament scholar Daniel Wallace defending the traditional authorship of the New testament manuscripts and their dating. It would be good for him to read a couple to get a perspective on where conservative scholarship lies.
I would also recommend he start using better sources. ( Apparently ) he may be using Dan Brown as a source and he thinks that canon was formed at the council of Nicea (A notion that even New testament skeptic Bart Ehrman thinks is laughably ridiculous)
1. How do we know we can trust the authors of the Bible?
We look at the testiomony of the early church fathers (external evidence) , the internal evidence and conclude who the author probaly was. We look to see if there is any early competing tradition. For example Early tradition is unanimous that the gospels were written by their tradtional authors. This counts as strong evidence for traditional authorship. You can look at Dan Wallace’s essays on authorship at the aforementioned site.
the gospels, for instance, were written 40 to 80 years after the purported resurrection
This is not true. Many scholars (including Dan Wallace) will argue for a dating between 50-65 Ce for the gospels.The strongest piece of evidence for this is the fact that Luke-Acts (the last synoptic gospel written) does not mention any major event such as the martyrdom of Peter and Paul or the destruction of Jerusalem that occur after 62 CE. That would be like writing a book about terrorism in America and not including the events of 9/11 . The only reason he would be likely to exclude them is that it was written before these events.
, at a time when the average life expectancy was 45 years.
First of all does this number take into account the high rate of infant mortality? Infant mortality could significantly lower the life expectancy. And what about wars where young men die?
he should check out this table
the figures say the average life extepectancy of your group tend to increase with age.
2. How can we verify the original documents, when none exist?
That my friend is the science of textual criticism. we have over 24000 new testament manuscript. We collate them , compare the readings and see which was most likely in the original.
3. Can we trust the translators of Jesus’s words?
Yes. Why shouldn’t we trust Jesus’ followers to accurately translate his words?
4. How do you know there aren’t lost documents which disprove Christianity?
I don’t know but I find it unlikely.
We know for a fact that the early Church sought out and destroyed documents critical of Christianity;
where does the author get this fact from? From what I know about early Christianity , the early Christian groups were hiding from Roman persecution and would be way too busy avoiding getting killed to hunt down heretics. Before Constantine’s conversion the Christians had no political power to do these sorts of things anyway.
whatever evidence these documents might have offered is now lost to us forever.
We do have information of these criticisms. We have the debates and letters of the patristic fathers where they respond to criticism. The most famous of these is Origen’s Contra Celsum.
And most of these works are not lost because a group tried to destroy them.People just didn’t seek to copy them. Imagine a time without Xerox machines where it would take days to copy books by hand. Papyrus and codices and ink were expensive and only a small group was literate enough to copy.Now if you were one of these Christian scribes would you spend all that money to copy
1)Your holy book
2)a book critical of your holy book
The Christians just didn’t copy this stuff. Why would they?
5. How can you trust documents which are known to have been edited by the church?
I agree that these have been edited but you forget , we do not only have 1 copy of the documents. We have copies from different chruches from Egypt to Greece to Rome. We compare the manuscripts from all these different churches and that way we can see if a particular church added something. How do you think we knew those additions were there in the first place?
6. Why do you have so much faith in a fourth century compilation?
The compilation of the New testament did not begin in the 4th century( despite what Dan Brown says). The core documents of the canon were more or less agreed upon by the 2nd-3rd century. And it was a more gradual process that 1 executive decision. A good article on the canon is here