Ephesians 2:8 faith is from God and no- there is no such thing as measure of faith for justification. That word used in Romans 12 is in different context. Jesus is fully God and fully man.
Jesus is the son of david and God.
2 Samuel 7:12-14
"I will raise up your offspring after you, who shall come from your body, and I will establish his kingdom. He shall build a house for my name, and
I will establish the throne of his kingdom forever. I will be to him a father, and he shall be to me a son."
This was a promise God made to David King of isreal about the coming messiah.
This was fulfilled in Luke 1;32-33 When Jesus was born, the angel said to Mary, “The Lord God will give to him the
throne of his father David, and
he will reign over the house of Jacob
forever, and of his kingdom there will be no end.
Luke 1:35, “The child to be born will be called holy —
the Son of God.
This had been quoted in 2 samuel 7 verse 13.