Verisimilitude

I'd like to expand on something I said about the recent debate between Bart Ehrman and Peter Williams:

https://www.youtube.com/watch?v=ZuZPPGvF_2I

1. For many years, Ehrman's stock argument against the reliability of the Gospels has been his contention that they were authored by anonymous writers decades after the events who never lived in Palestine. But in the debate he suddenly shifted grounds. He said that even if they had accurate background knowledge of 1C Palestine, that creates no presumption that the accounts of Jesus are accurate. 

2. To begin with, I don't know what Ehrman is claiming. Is he claiming that the Gospels are intentionally historical, but the writers are simply clueless about the historical Jesus, despite their intentions to write an accurate biography? If so, why would their sources be accurate about little background details but wrong about the main events? Why would their sources preserve accurate background information but be unreliable about the main events?

3. Apropos (3), it's unclear on Ehrman's reckoning how we could ever credit any ancient historical account. If incidental accuracy in details doesn't count as evidence for the general accuracy of the stories, then how, if at all, does Ehrman distinguish between legend and history? Doesn't his skepticism apply with equal force to Thucydides, Julius Caesar, Tacitus, and Josephus (to name a few)? Isn't the kind of corroborative evidence Williams marshals in Can We Trust the Gospels the same kind of evidence historians use to verify ancient accounts generally?

4. For that matter, if he's that skeptical about ancient records, then he can't say the chronology in Lk 2 is mistaken, since he'd have to have confidence in other historical sources to use them as a standard of comparison. 

5. Or is he claiming that the Gospels are intentionally fictional, but the Gospel writers sprinkled their stories with accurate background information to lend the stories verisimilitude? If that's what he's angling at, then one problem with his objection is that what he says about the authors is applicable to the audience. Verisimilitude is only effective if the reader is in a position to recognize the accuracy of the details. If, however, the Gospels were written decades after the fact by authors who never lived in Palestine, or knew people who did, then wouldn't the target audience for the Gospels be in the same boat? The audience would be just as uninformed as the authors. So how would they be in a position to appreciate verisimilitude? Wouldn't accurate background information be lost on them? 

6. As I mentioned before, it would dangerous to be a Christian back then. Why would the Gospel authors risk writing fiction that was so hazardous to their life and livelihood? If, on the other hand, they were writing historical biographies, then it would be worth the risk, given who Jesus is. 

7. Ehrman kept defaulting to memory studies. But in his recent book, Christobiography, Craig Keener devotes a whole chapter to that issue (chap. 14). Likewise, Richard Bauckham's article: “The Psychology of Memory and the Study of the Gospels. ”Journal for the Study of the Historical Jesus 16 (2018) 1-21.