Realization #3 - controlling too many governments too quickly can easily leave you strapped for cash and pulled in too many directions.
Good report! I think you'll get much enjoyment out of Imperial. I know I have.
I agree with most of your realizations, but I think #3 might not always be true. When you control countries, you control when they "investor" and that is how you can "milk" them for money. If you control a lot of countries, then it might be best to continually try and get them on a Tax and Investor "spin." Your general gist of being pulled in too many directions can be correct. When I teach the game to new players, I usually point out that the game can be easier to focus on if you have an "enemy." This means not investing in every country, because you need someone to beat up on without it directly hurting yourself.
That being said in a 3-player game, you might find you have bonds in every country, and then you focus on fighting the countries where you have the lowest investment, because it will hurt your opponents the most.
Good gaming and welcome to the Imperial bandwagon!