Why are you ignoring the obvious? It simply is amazing how often anti-Trinitarians will quote this verse and miss the obvious. But this is even worse since you are, correctly, showing that 1 Cor 8:6 is Paul's expounding of the Shema, but you've only made half the argument.
Deu 6:4 "Hear, O Israel: The LORD our God, the LORD is one. (ESV)
1Co 8:6 yet for us there is one God, the Father, from whom are all things and for whom we exist, and one Lord, Jesus Christ, through whom are all things and through whom we exist. (ESV)
You cannot highlight "one God, the Father" and then leave out "one Lord, Jesus Christ". Both are a part of the Shema. And, of course, if you use this verse to say that Jesus therefore cannot be God, then logically one must conclude that the Father cannot be Lord. But we know the Father is Lord, so these are not exclusive terms.