Hi Waiting,
Re your supposition that Abraham, Isaac, Jacob, Melchizadek, & others were also monotheists, consider this.
This presupposes that the Bible is true and the writers were above skewing the stories, which, of course, is debatable.
Now, we know that MOSES wrote the Pentateuch--Genesis thru Deuteronomy, which contains the stories of the above people. He could have simply wrote it so that the others believed ONLY in Jehovah--backpedaling the saga in order to fit his beliefs.
The following may support that:
1. Abraham came from Ur which was one of the chief city-states of Sumer. He could have easily been polytheistic.
2. Rachael's family was polytheistic, as you brought out recently on another thread. She stole Laban's gods.
3. "Elohim" is used to refer to God often in the 1st 5 books. It is plural. The WT and others explain this to mean magnificence in Hebrew language. It also could have simply been plural.
What do you think? There may be more possibilities in this line, huh?
Pat