The only way we can come to understand what John means in John 1:1 is to consider the whole of John in its entirety. If we focus solely on one verse then its too easy to come to an incorrect conclusion. You have already acknowledged there is an aspect of distinction between God and the Word. We simply understand the 'WAS God' differently. I've provided sufficient scripture within John to argue that Jesus is the Son of God as distinct from God.
The argument based on reason is simple logic (ironically another meaning of the Greek word logos) that an infinite God is uncontainable, especially in the finite physical form such as a human body. Scripture once again echoes this argument:
But will God indeed dwell on the earth? behold, the heaven and heaven of heavens cannot contain thee; how much less this house that I have builded? 1 Kings 8:27
The only explanation of Christ's Divinity that makes sense IMHO is that Jesus reflects God's attributes perfectly. St Paul appears to support this view.
But we all, with open face beholding as in a glass the glory of the Lord, are changed into the same image from glory to glory, even as by the Spirit of the Lord. 2 Corinthians 3:18
In whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them. 2 Corinthians 4:4
In whom we have redemption through his blood, even the forgiveness of sins:
Who is the image of the invisible God, the firstborn of every creature
Colossians 1:14-15