"scriptures instructing Christians to witness for CHRIST, and not for God."
The scriptures instruct no such thing.
Think about the context.
The scriptures you listed was because the person of Jesus was new to them. They had to proclaim him and what he did and what it means because it was a new thing. But that did not change who the Israelites were and thus who Christians were in relation to Jehovah God.
Don't get the Witnessing for Jesus and Witnesses of Jehovah confused. It is not about what all these scriptures say. It is about understanding how Jehovah and his son Jesus function in the Genesis to Revelation.
Stop trying to find fault with the teachings, it won't work.