Hi,
Are you a Jehovah's witness?
Because those arguments you use are what the JWs use.
Here is a link which includes CH Dodd whom you have mentioned about what the Greek scholars really think what John 1 V1 means
No webpage found at provided URL: http://www.equip.org/free/DJ520.htm
Furthermore
No webpage found at provided URL: http://www.bible.ca/trinity/trinity-Dodd.htm
There is only one God according to the bible, but the personhood of Jesus means that he was fully a man and also fully God.
But thats only part of the story. You say from Galations 3:20 that God is one person. The actual Christian doctrine of trinity states at its core
one God
Father,Son,Holy Spirit, each God
Father,Son,Holy Spirit each distinct
All throughout John, Jesus links himself with Yahweh:
Eg John 8:58-59,John 18:5-6 When Jesus was asked to identify himself, replies "I am", they all fall backwards at the shock and power of those words.
If you are willing, I can send you some notes on the trinity which should clear this matter up?
Best Regards
Mike King