Well, in the passage above, God is setting down rules to govern polygamy, so yeah, He's sanctioning it. No question about it.
No; He’s saying how to deal with it IF and AFTER it happens.
“I’ts not good for man to be alone” didn’t mean for him to have more than one.
Adam only lost ONE rib...
To Adam he said, “Because you listened to your wife(s?) and ate fruit from the tree about which I commanded you,