Sorry, but both your examples of Lamech & Nahor weren't deemed as part of that new nation of Israel. (You flunk Old Testament history)
There's absolutely NO proof offered up by you that as of Deut. 25, that Moses had 2 wives...As a matter of fact, he was as of Deut. 25 married ONLY to Zipporah...and there's absolutely no proof offered up by your presumption that Zipporah was still alive when Moses LATER married a Cushite woman.
Your Amram-Jochebed-uncle triangle was a "joke-in-bed" right?
And we KNOW that NO other woman was accorded WIFE status to Abraham other than Sarah...and Ketureh AFTER Sarah died.
In Gen. 16, Abram, the Angel of the Lord and Hagar herself reference her as ONLY a servant of Sarai. Moses does the same in Gen. 21; and so does Paul in Galatians 4.
Likewise, so does Sarah AFTER Hagar slept with Abram.
All of that, btw, was evidence of DISTRUST in God...they didn't believe that God could ensure that an aging Sarai would become pregnant.
You have floundered greatly. NO proof ... at all...that polygamy was in practice by covenant Jews by Deut. 25 other than by deception & then wifely rivalries (Gen. 30)... and the temporary sleeping arrangements of Gen. 16 was by distrust in God's promises....in which neither Abram, the Angel of the Lord, or even Hagar herself reference Hagar as the "wife" of Abram!
And we KNOW that NO other woman was accorded WIFE status to Abraham other than Sarah...and Ketureh AFTER Sarah died.
To be his wife.