I'm not exactly a biblical scholar, but I did attend a lecture in my ancient civilisations course about the genesis of Christianity and do have a full basic religious education from high school:
Before I begin, a couple of things about the Bible: First of all, it is a collection of books decided upon by Roman meeting (of Church officials, government officials or both I'm not sure) several hundred years after the death of Jesus, and there were many other holy texts that may have been a part of it at the time. Secondly, everything must be interpreted before you can reach any true meaning. At face value, almost everything in it either contradicts with modern day ideas or virtues, contradicts something else in the Bible, or is merely a part of the story (person X went to town Y). The problem is that what the "correct" interpretation is can be very difficult to know thanks to the wide range of interpretations available, the limited evidence we can obtain through historical studies, and the ways in which it has been translated from language to language over time.
To your questions:
1. You're correct, Bethlehem is only mentioned in one book. This falls under the category of "contradictions something else in the Bible" and is either something you need to think about for yourself. I would encourage you speak to an actual religious scholar if you want more of an answer, probably even a priest.
2. There were actually two Roman censuses around this time, one shortly before and one shortly after 0CE. Both had a king Herod (I think it was Herod) ruling at the time, which is also mentioned in at least one of the books.
3. You're correct there, but there's nothing more I can add.
4. I can't help you here at all, sorry.
At the time of Jesus, there were a lot of miracle workers going around performing miracles, and there were many religions kicking around at the time, all with their devoted believers (which is funnily enough mirrored in Life of Brian's two radical groups of the Judean People's Front and the People's Front of Judea).
Scaredgirl, I've also watched Zeitgeist, and it it is indeed a very interesting film. I heard at some point that the first few books of the Bible, or possible only Genesis, was written after the Jews fled Egypt as fiction in order to teach people about the nature of God, similar to the image of Jesus as a 'perfect human'. The problem with the way Zeitgeist presents the arguments about the many similarities of different religions is that it fails to mention all the interactions these religions had over the years, and I *think* that *some* of its facts or connections with the other religions are outright untrue, but can't recall any specific examples. Some common Christian ideas, such as the standard definition of Hell and the devil, were taken directly from other religions in order to help convert people, but are re-interpreted back out of existence upon further inspection (Catholicism: Hell isn't a place of eternal suffering, but rather afterlife without God. Jesus went to Hell when he died, but this is usually omitted because of the standard idea of Hell). Unfortunately, Zeitgeist is the only place I have seen any discussion of these ideas in relation to Jesus, so I find it difficult to form solid opinions on the matters.