On the topic of whether morality is internal or external, surely external morality is no morality at all. If you think morality comes from God, then what if God came down and told you that he had changed his mind, and now wanted you to do something which you had always considered immoral? The Bible speaks specifically to this question, and gets it completely backwards. The story of God commanding Abraham to kill his son Isaac is supposed to demonstrate that it is always right to obey God, no matter what God says, but in fact that is exactly the opposite of the truth. If you would kill your child because God told you to, then you are an immoral person. No reasonable moral person could disagree with this, and that is clear because all the good, upstanding, moral men and women who wrote our laws never put a God exception into the murder statutes. "Oh, ma'am, you drowned your child in the river because God told you to? Okay, well then go free!" That would be absurd. Nobody believes that.
Your morality comes from within yourself -- both figuratively and literally. It comes from your brain.