God used his proper name, "YHVH", to show that it was "YHVH" who made the heavens and the earth and all that is within them. It appears to be in the third person because "YHVH" is translated as "The LORD."
There is no break in the conversation in Exodus Chapter 20. The Ten Commandments were given to Moses without Moses putting in any commentary. Those were the words spoken by YHVH. Those were the words etched by the finger of God on the stone tablets.
Your problem is that you cannot reconcile the fact that God himself took credit for making the heavens and the earth and all that is in them in six days. It doesn't jive with your evolutionist philosophy, so rather than accept the word of God, you reject it and cling to your evolutionist philosophy.
Well the fact is that God said it. There is not a single legitimate manuscript that does not contain that language. It was not a part of "oral history" since it was written from the time of Moses. So either Moses was a fraud, or God made the claim.
Which premise do you accept?
Tough decision. The Bible is not the literal word of God, or God condones slavery. The Bible is not the literal word of God, or the universe itself is a lie.