On the topic of OT prophecy and things like the "Triumphal Entry" I am split. On one hand, I appreciate the argument from redundancy in that if it was thought of as something the messiah would do, we cannot say for sure that Jesus actually did it (since the gospel writers/rumormongers would have wanted such details to fill out the story). On the other hand, if we do posit an HJ, then he must have done some thing or some things during his lifetime which convinced his followers that he was the messiah. I have yet to see a strong enough argument for the "suffering servant" being interpreted as messianic pre-Christianity (although I am open to the possibility), and find it much more likely these beliefs about him developed before the crucifixion (and then cue cognitive dissonance). So little things like riding into Jerusalem on a donkey could theoretically fit the bill of someone who wanted to give off that he was the One foretold.
On another note, I am hesitant to attribute any atonement theology to Cephas or any of Jesus' relatives/followers. That might be a Pauline innovation. I'm particularly struck by the Didache, which lacks any talk of Christ's atoning death when describing the Eucharist.
