First let me say thanks for the points you made. It is helpful stuff and I will have to chew on a lot of what you wrote
History:
Those who argue for Paul's admonitions to Titus and Timothy as specifying monogamy for Deacons and Elders are crucified on their own logic. The very fact of limiting it for a specific group (if that was even Paul's intent, which is dubious), acknowledges both it's acceptability and practice amongst the group at large.
In response to this one point of yours I wanted to propose that there is no mystery about exactly what Paul meant even if there was no polygamy being practiced.
The Titus and Timothy requirements are better translated "one woman man" instead of "the husband of one wife". These requirements/prohibitions come in the midst of a list of known sin issues (known to anyone who knew Torah).
People (especially those who think Torah is being replaced by new post-christ rules) assume Paul is adding new laws for God's people. I will assume
we can agree that Paul never intended to add new laws to Torah. So that leaves us with "one woman man" must mean Paul was forbidding the church from having leaders who were "several woman men" in a category that would already be known as wrong in Torah. That means ongoing serial fornicators, serial
monogamists as well as adulterers were barred from this type of leadership.
As a second witness to the meaning I understand that the Greeks of the time would have had all three of those types of sinners in good supply. They would not have had polygamists in good supply, so for Paul to be addressing polygamy in those passages seems highly unlikely (based on the original intended meaning of the writer to the original recipients).
As a second proof for the meaning Paul never elsewhere mentions polygamy as something he is concerned about among the gentiles. He does however speak a lot about men who commit fornication as an ongoing practice, adultery and incest (ungodly "several women men").
There is no way in my right mind I can consider Paul to have intended to put polygamy in a list of condemnable lifestyles. He would have been throwing Abraham and David under the bus in written form to circulate to the churches. He would have rather barfed on himself.
I hope none of this is coming off ruff, I'm just passionate about it. I'm also a little pissed at the translators.
Also as I have studied gentile marriage culture in the first century Mediterranean. I have read several times that they didn't practice polygamy. I am not able to read source texts to come to that conclusion so I am taking people's word for it, but it seems accurate.