How do you divide Christ Jesus' human nature from His God nature?No need to "divide" them. Christ has a dual nature, as affirmed in the Athanasian Creed.
Christ received His divine nature from His perfect, divine Father, and His human nature from his human, fallible mother.
Here's a good explanation. Read it and learn...
THE DUAL NATURE OF JESUS CHRIST
Nothing unorthodox that I can find in that article. The Nestorian heresy, however, effectively separated the two natures, when the truth of the matter is they are united in Jesus' one Person. That's the crucial point on which the truth of "Theotokos" hinges.
Jesus Christ, the Person