Firstly, one thing you can find out about God, is that he is a very Jealous God, the first of the 10 Commandments is to have no other gods, not purely because hes a selfish God, but because he wants us for himself, if we are found to be worshipping the Devil in disguise, he knows the Devil can laya claim on us.
In Haggi, it is quite specific that God will reject even true and clean worship if it is contaminated by false worship.
Hense, if people dont take the Bible as literally as they are able to understand it, people are free to make thier own religions which if they do not conform to Gods idea of his religion, they would miss out on the rewards of belonging to God.
In effect, without a literal guiding book, you could just make up a religion, say its from God, and who would know?
So, we have no choice but to take the Bible literally.
If you read the Bible a lot, it does actually harmonise, but in a deep way.
What you said about the violence of the Old Testament can be viewed like this for instance.
We left God at Eden, we no longer have any place on the planet he made, its his world, he can chose who he wishes to live on it, hense, for enemies of God and his people, the world is a dangerous place and he is a dangerous God.
The law given to the Jews demonstrated that even when God told us how to behave, we couldnt.
Hense, the old testament has given us this picture of the real implications of Gods promise to Adam as to what would happen to man if he disobeyed.
Then, along comes Jesus, one of the parables of Jesus was of two men who owed money they couldnt pay, one a litlle, the other a lot, both where let off, Jesus said that the man let off a lot, would Love his benifactor a lot more than the one a little.
So, Jesus has taught that though we dont deserve salvation, God is so loving that hes going to let us off the heavy price for our sins that the Old Testament showed us, by Jesus himself payin the price with his death.
The result being, we feel so gratefull to the Love of God and to Jesus as well, that it is our Love for them, that makes us try to be good, not just selfish self preservation.
Another clue about the Bible, its written in a sort of code, I dont mean like numerology, but in a way that you can only see it if you really look hard and God helps you, this is what Daniel said about his own writtings in the book of Daniel.
Chapter 12
4But thou, O Daniel, shut up the words, and seal the book, even to the time of the end: many shall run to and fro, and knowledge shall be increased.
8And I heard, but I understood not: then said I, O my Lord, what shall be the end of these things?
9And he said, Go thy way, Daniel: for the words are closed up and sealed till the time of the end.
10Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and none of the wicked shall understand; but the wise shall understand.