1.
This is how google defines divine;
Adjective
Of, from, or like God or a god.
Noun
A cleric or theologian.
Verb
Discover (something) by guesswork or intuition: "his brother usually divined his ulterior motives".
Although you can see that the very definition of the word divine allows for more possibilities than just literally being God, the Gospel does portray Jesus as more than just an ordinary mortal, after all He is the mediator between God and man.
So basically I would explain the divine nature of Jesus using the following comparison;
Consider a person in a dark house on a day where the sun is out. Through the window this person looks into a mirror angled towards the sun. In this mirror he sees the image of the sun, and in this mirror the physical attributes of the sun (light and heat) are reflected.
Now the person is like you or I, the perfect mirror is like the perfect soul of Jesus. The spiritual attributes of God (love mercy etc) are manifested through Jesus like the reflection of the attributes of the sun in a mirror, whilst the Holy Spirit is like the rays of the sun which reach us from God through Jesus.
In the same way the physical sun does not descend from it's exalted position in the heavens to dwell in the mirror, so also God does not literally descend to dwell in Jesus.
c) Assuming hypothetically for the sake of the discussion that the virgin birth is a direct copy of the Augustus story, it does not necessesitate that Jesus was literally God, for example it is just a miracle, and many miracles were attributed to the other Prophets, but they weren't seen as God in any trinitarian sense.
Also if it was copied, we don't know the aim of why, for example it could have been copied to give Jesus wider appeal amongst the Romans. The Qur'an has the same virgin birth story as the Gospel and yet I'm sure we are agreed that the Qur'an doesn't claim Jesus is literally God, so you can see that it doesn't follow of logical necessity of it being a copied story that Jesus was literally God.