If I am asked to write a constitution (hammach once started such project), I will not write the US Constitution word by word, not even thought by thought. Does it mean I don't support the US Constitution?
The criterion of support must be "agreement to live under given a choice not to".
Our US Constitution does enjoy such support from 100% of the US citizens by definition of citizenship.
I propose replacing your (3), which I just rendered tautological, with mine:
(3A) Allow inimpeded renunciation of citizenship and freedom of emigration.
"...given a choice not to" is subjective. There are real life dilemmas where two options are available, but each seems equally unacceptable.
I spend my life savings and several years of my own labor to build a home and a productive farm, but the home as I wanted it is not marketable at near the value it is to me. My parents and in-laws are elderly and live close by where I can care for them as circumstances denmand. My children and grandchildren also live close by. Now, because annalex and 90 of his friends decide to form a government and draw "national" boundaries which incorporate my home and the homes of my loved ones, and they decide that smoking, alcohol, cursing (blasphemy), high cholesterol foods, firearms, and non-"organic" milk will be disallowed, taxes will be imposed to build a water and sewer system for the whole republic (I have a well and septic system that function quite well). Where is my choice? (3A) Allow inimpeded renunciation of citizenship and freedom of emigration.
As above, there are all kinds of circumstances which make the unobstructed-by-govenment "freedom" of emigration have no resemblance to freedom of choice (about things which affect no one but me and mine.)