1. Does adding someone to a coalition who has low popularity bring everyone else in the coalition down? That seems to be the case in the game I am in.

2. Is your popularity attached to your account so it carries over from one game to another?

3. Will booting someone from a coalition who is low popularity bring others back up?

4. Does this procedure work to keep your popularity high: a) declare trade embargo, b) wait for day change, then declare war, c) wait for day change, then attack. If so, can the declarations be a few minutes before day change, or is it necessary to wait an actual 24 hours?

Yes, I've read that thread. But here are some facts:
1. In my current 100 player game, I started the game at 83% popularity. Don't know why it wasn't 100% or 0% or anything - it was just at 83% right out of the starting gate.
2. I trade embargoed a neighbor a few hours before day change on day one.
3. I added someone to my coalition who had a popularity somewhere in the 70's.
3. On day two, I noticed my popularity had fallen to 74%. Then I did a few market trades of low amounts just to see if it would have any effect on my popularity.
4. Just before day change on day two, I declared war on the neighbor. Then I waited until day change was over and then gave orders for attacking movements.
5. Now as day 3 is almost over, I notice my popularity is still 74%. I just noticed the neighbor I attacked, who did not initiate any wars with anyone has a popularity of 21%.

So I don't know how to explain any of the above. That is what stimulated my questions, plus in the thread you recommended and in other threads about the subject I noticed other players referring to actions they took in previous games as if it had effect in their current game.

So I am greatly confused.