He shall not have many wives, that may allure his mind, nor immense sums of silver and gold. (Deuteronomy 17:17 DRC1752)
in every situation you mentioned bad things happened. The Jacob’s wives fought and got jealous, God clear disapproved of what Abraham did with Hagar, other wives fought for their husband’ attention, etc. polygamy is not portrayed as a good thing
The reference in Deuteronomy is to kings such as Solomon who had 700 wives, many of whom were foreigners and led him astray. This is not a blanket prohibition of polygamy.
Also, what exactly did Abraham do to Hagar? It was Sarah, not Abraham, who drove her into the wilderness. But God blessed Abraham’s offspring from both marriages. The angel told Hagar (Genesis 16:10) "I will so greatly multiply your offspring that they cannot be counted for multitude.” And God appeared to Abraham and Sarah (this was after Abraham was also married to Hagar) by the oaks of Mamre and told them that Sarah would bare a child. And when Abraham obeyed God and agreed to sacrifice Isaac, God said to him (22:16018), "Because you have done this, and have not withheld your son, your only son, I will indeed bless you, and I will make your offspring as numerous as the stars of heaven and as the sand that is on the seashore. And your offspring shall possess the gate of their enemies, and by your offspring shall all the nations of the earth gain blessing for themselves, because you have obeyed my voice.” There is never anyplace in Genesis where God told Abraham that he disapproved of him having more than one wife.
Abraham’s brother Nahor also had a wife Milcah and a concubine Reumah and according to Genesis 22: 20-24: “Now after these things it was told Abraham, ‘Milcah also has borne children, to your brother Nahor: Uz the firstborn, Buz his brother, Kemuel the father of Aram, Chesed, Hazo, Pildash, Jidlaph, and Bethuel.’ Bethuel became the father of Rebekah. These eight Milcah bore to Nahor, Abraham’s brother. Moreover, his concubine, whose name was Reumah, bore Tebah, Gaham, Tahash, and Maacah.” Does any of this sound like God disapproved of polygamy?