HeadinHands, the mainstream Christian understanding of the relationship between the Old Testament and the New Testament is that there is only one God -- the God whose name is 'I am', the God who created everything, whose name means 'all' in the language Jesus spoke.
The Old Testament tells the story of how the Israelites came to see that there is only one God, and became the first monotheistic people -- this was their religious genius. Over the course of the OT, through their history, and through the prophets who interpret their history to them, they come to see that God doesn't desire sacrifice but worship, and that he wants them to be a holy people.
The New Testament tells the story of God's revelation of himself in Jesus Christ, his fullest revelation of himself and his purposes for humanity. Jesus's own message is that the Law is fulfilled in two commandments love your God with all your heart, mind and strength, and love your neighbour as yourself putting love rather than justice, which is the centre of the ethics of the OT at the heart of his revelation of God. The rest of the NT shows how, after the resurrection, Jesus's followers came to see that his message had to be taken to the Gentiles, and that the whole earth not just the Jews -- could be God's holy people.
The Bible isn't divine in the sense of being written by God. (Now answering point made by you yesterday.) It was written by human beings, and tells of their experiences God. God can only reveal himself to us through the medium of human perception, imperfect as it is, and the Bible is, among other things, about the way that a particular group of people, over time, came to have a truer idea of what God was telling them. To understand the OT properly you have to see it whole -- simply focusing, out of context, on a few shocking episodes gives a false and distorted picture. And these shocking episodes need to be understood in the light of their context, the history of their composition and their literary genre before we can see them clearly.