The Bible Is God-Breathed

As for the Bible being the source of truth, the Bible is God-breathed in that God breathed out His words to us, as opposed to people wrote down some words and God breathed on those words to give those words his endorsement. It's seems to be a subtle difference, but it makes a world of difference because the former is infallible but the latter is not. Moses was not there during Genesis but it was God who gave these truths to Moses. The Bible is directly from God and it is believable that God can communicate this to us through various individuals because if God really exists, He can do anything. He can raise people from the dead, and He can certainly see to it that His truth is communicated to us in the form of a Bible even if some of the authors weren't eyewitnesses. As far as the books that are included in the Bible, there was an entire process by which the books in the Bible were chosen, and certain other ones not included. All of the Bible is from God, written by the people God spoke directly to or close associates of those people. It is true that the Old Testament should not be read with the intent of following all of it down to the letter, because none of those laws apply anymore, since we have been given a New Covenant through Jesus, which frees us from that law.

For sure there are copyist errors. If we start with one copy, let's say they copied it 4 times to distribute it to the north, east, south, and west. Then in each of those places, they make four more copies to distribute again to the north, east, south, and west, and so on. During this multiplication of copies, somebody may have missed say a word in the fifth generation of copies, but that word should be there in the third generation. That's why we compile and look at as many manuscripts as possible to verify and validate the text. In this sense, the Bible is the most accurately transmitted document; it has the most manuscripts and fragments from various geographic regions, which together reconstruct the same, repeated information and ascertain its reliability. To reject this, one would have to reject all the other ancient texts because none of those come close to the transmission accuracy of the Bible. 

As far as malicious tampering of the contents of the Bible, let's say there were an evil person who wanted to alter some part of the Bible. That evil person would have to make sure to go to the north, south, east, west, and everywhere else the copying was being done... Probably not possible (evil person argument thanks to M. Slick).