If Jesus is God, then how can He not be the Father? Do you believe in more than one God?
High Priest is a role of Messiah. Yet He is also a real High Priest. So no contradiction between role and "real". Son is a role, and He is also a real Son. Again, there is no contradiction between the two.
Believing in the Son is about believing the man Jesus is the Christ, the Messiah, resurrected and immortal, the covering for our sins, our King and Priest, and indeed "God manifest in the flesh" and our Great God and Saviour.
Again, I think much of the difficulty here is the language issue. When you hear "God became a man" I think you might be misunderstanding what is intended.
And the word became ("was made") flesh. Flesh here doesn't just mean physical, it means the logos became human. Jesus is not just a physical body, He is a genuine and complete human being.
So the logos became a man.
But, the logos is Theos. Therefore, God was made flesh, which is the exact same as saying God became a human being.
The Bible says the LOGOS was God, and then became flesh. Therefore God became flesh. And flesh is not just skin, but human nature, ousia. So The Logos (which was God) became a male human being, anthropos, andros. And we saw His doxa, as of the only begotten Son.
The Son is Immanuel - "God-With-Us". He is God manifested in the flesh. He is the visible image of the invisible God, He is the True Ikon of God.
It is confusing to say "the Son is the Father" because people get confused by that. Jesus is the Son. But the Son is God-Incarnate, God manifested in human nature. So Jesus is also the Father (because He is God, and to us there is one God, the Father). As Isaiah said of the Son "His name shall be called the mighty God, the Father unto the age". (
Isaiah 9:6).