Q. Is Jehovah only the God of Jesus the Mediator Man?

Ephesians 1:17"that the God of our Lord Jesus Christ, the Father of glory, may give you a spirit of wisdom and of revelation in the accurate knowledge of him."

Hebrews 2:7 is a scripture quoted to show that since He was made a little lower than angels it makes sense to say that had a God over him
"You made him a little lower than angels; you crowned him with glory and honor, and appointed him over the works of your hands."
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He can't still be a human in heaven because human bodies don't exist in heaven.

1Corinthians 15:47,48" The first man is from the earth and made of dust; the second man is from heaven. Like the one made of dust, so too are those made of dust; and like the heavenly one, so too are those who are heavenly."

When Jesus became man, he left behind his heavenly body and adopted a human one. Once he completed his mission of dying for our sins, he gained his heavenly body back.

[After the ascension] Revelation 3:12 The one who conquers—I will make him a pillar in the temple of my God, and he will by no means go out from it anymore, and I will write upon him the name of my Godw and the name of the city of my God, the New Jerusalemx that descends out of heaven from my God, and my own new name.y 

Hypothetically, even if Jesus was still a man in heaven, it wouldn't matter because he was placed at God's right hand.

Ephesians 1:20 "which he exercised toward Christ when he raised him up from the dead and seated him at his right hand in the heavenly places, "

1 Peter 3:32" He is at God’s right hand, for he went to heaven, and angels and authorities and powers were made subject to him.

So even while he was exalted to the right hand of God, he was still referred to as having a God.

Revelation 1:6"and he made us to be a kingdom, priests to his God and Father—yes, to him be the glory and the might forever. Amen."

Ephesians 1:3"Praised be the God and Father of our Lord Jesus Christ, for he has blessed us with every spiritual blessing in the heavenly places in union with Christ"

1 Peter 1:3"Praised be the God and Father of our Lord Jesus Christ, for according to his great mercy he gave us a new birth"