Mdd,
1. You heard (or remember) wrong. Abarbanel lived two generations before the Shulchan Aruch. Thus he is a Rishon. Anyway, Rambam says that it is a mitzva to appoint a king not an obligation. Giving a get is also a mitzva.
2. The Gra, the Shaagat Aryeh, the Schach, the Peri Chadash and the Chazon Ish did not accept that. See “??? ???”? ??? ?????? ????? ???? ???? ????? ?? ????????” )on-line) for a discussion of this issue.
3. Yes. That is why He gave limitations. He also gave alternatives.
4. You still have not answered my kushiyot. Why did it take 355 years to appoint a king? How were the leaders in EY after the Churban called nesi’im and not kings?
5. See “The Source for Elections in the Torah” by Rav Mordechai Greenberg (also on-line).