I can understand your confusion. Yes those things did happen in to Old Testement, and in the New Testement they don't. The reason for this is simple. God didn't change. Yes these things happened but not because he wanted them too. They happened because of leaders at the time twisting the word of God. There was a time when the average man wasn't even aloud to read the word of God for the leaders at the time said it was sinful to do so. The people relied on their leaders (religous and political) to tell them how to live. So these things happened. But once Jesus came here to tell us all we were doing it wrong things changed for all religons. Even if you were not a follower of Christ at the time you knew he was right. He came and basicly told the world that this was not his father's (his) way. It was one big slap upside the head from God saying "what were you thinking?" And the whole world changed after that. So what i am saying is God doesn't change, we do.