> That the idea of God wasn't started until 200 BC.

Since you're asking, no, this is not true. The Septuagint was translated from the Hebrew text between 300-200 BC, so we know the idea of God was around before then.

A silver amulet from the 7th or 6th c. BC was found of Numbers 6.24, so we know the idea of God was around then.

The name YHWH appears in the Mesha Stele (840 BC). So the idea of God was around before that.

> Joshua did not say, "As for me and my house, we will serve God". He said "We will serve JHWH".

This is true, but YHWH was also known as God (Gen. 2.4; Dt. 4.35; 1 Ki. 8.60).

> This deity was the titular deity of his tribe, and acted more of a supernatural mascot than anything

This is not true. Through the OT, God is often portrayed as the suzerain of his kingdom and people, as well as the Lord of heaven and earth, God Almighty (el Shaddai), and as the Divine Warrior, not as a supernatural mascot.

> even the idea of Adam and Eve and the Garden and Serpent was not known until around 600 BC.

Because documents and artifacts become fewer as we go back in years doesn't mean the idea of A&E was not known until around 600 BC. Frankly, there's no way to know such a thing, based on current discoveries, so you can't say this with any confidence.

> If there was an actual Abraham, he would have had no concept of Adam and Eve.

Same as the previous comment. You can't know this. We don't know if there was; we can't know if there wasn't.

That the idea of God wasn't started until 200 BC. The concept developed gradually over the years to become what we think of today. Joshua did not say, "As for me and my house, we will serve God". He said "We will serve JHWH". This deity was the titular deity of his tribe, and acted more of a supernatural mascot than anything and even the idea of Adam and Eve and the Garden and Serpent was not known until around 600 BC. If there was an actual Abraham, he would have had no concept of Adam and Eve.