Jesus was a Jewish Rabbi. He's claimed by his followers to be the Jewish Messiah. He's quoted in the Gospels as adhering to the OT. He was a Jew and spoke within Jewish customs. He had a few disagreements with how the Pharisees were running things, but he never spoke contrary to his own faith. Ergo, I disagree with your assessment that the OT has nothing to do with Christianity.
OTO, I think we can agree that the Evangelicals, Prosperity Christians, Westboro Baptists and other like-minded groups are not following the principals of Jesus as given in the four Gospels.
Agreed on the "2 completely different Gods" point. It's easier to understand when it's remembered that it was humans who wrote the books and who selected the books.
The OT is not the Hebrew "bible". It's an edited version cherry-picked centuries later except for the first five books (Moses). While I agree this was done for control, given the times, it was an advancement in civilization.
Anyone who think human beings would be where we are today without religion is a fucking moron. Sure, there are negatives involved. Two steps forward, one step back. It's still advancement that, IMO, would not have taken place otherwise. Human nature being what it is. LOL