The fact that the Bible has been rewritten so many times is actually an argument in favour of the accuracy of our modern manuscripts. The more copies there are in circulation, the less the odds that a transcription error in one single copy is going to spread, since there's so many accurate copies to compare it to. Add to that the fact that the monks who painstakingly copied it by hand were fanatically devoted to their work, taking many hours to copy a single page, and checking it over many times in great detail before authorising it, you get a very good rate of transmission. Orders of magnitude greater than any other contemporary literature, at any rate.
Regarding translations: the reason no translation is 100% perfect is that certain words in other languages encompass different ranges of meaning than English. For instance, the Greek word
pneuma means both a breath of air and a spirit or life-force. We don't have a single English word meaning all that, so we have to make do with "spirit" or "breeze" depending on the context. This is why concordances with Hebrew/Greek lexicons are so popular -- with them, you can look up the full meaning of each Hebrew/Greek word in the Bible.
So yes, while it might be harder for us English-speaking Westerners to get the full meaning of the Bible than it might have been for Greek-speaking Jews of the first century, it is possible and not really all that hard if you try. Translations like the Amplified Version do a very good job of getting at the full meaning of the original languages, by including alternate translations of certain words in brackets right in the text.
As I said earlier in the thread, it works out pretty well if you use months rather than years (with an average date of death being 70-ish), but the whole thing goes south when you realise that, using those calculations, most of the people would have been having kids at 8 years old.
The waters above would be the clouds -- the source of rain. Some postulate an additional layer of water vapour surrounding the planet, like an extra ozone layer, but this is a matter of some contention within the Christian scholastic community.
As for Revelations, it can be rather confusing for modern readers because it's written in the style of first-century Apocalyptic literature, which was a highly symbolic style. It kinda has a reputation as the "most confusing book of the Bible". That's no reason to stay away from it, though -- just to be prepared.
