Dear Jedi,

Don't get caught up in a bunch of false nostalgia from Hollywood movies.
You were born American, as were your kids; unless you intentionally give up your citizenship you will always be American. Look up the word "perspective" on Wikipedia; it is a choice and it is a wonderful thing.
Regardless of how long you are gone, it will make you appreciate America, for its grandeur and its warts; but from a different perspective. I read a recent WSJ article saying there are now 6.3 million expats (and that's not counting active military) so there must be something to it; admittedly it's not for everyone.

In answer to your questions:
Left with my partner by choice; no kids; I'm sure that made it easier, though I know lots of people that have very well adjusted kids here; we are in Western Europe;our IT jobs offer more flexibility than other careers; there is a period of cultural shock; No Walmart at midnight and that crazy idea that people should have a life work balance!
Been here 10 years; there is a frustration almost every day;
there is a joyous moment almost every day; it's our attitude about it that makes it work ! We treat it as an adventure.

You are on the right course; research, research, research!
The more you learn beforehand, the less surprises.
Your idea about a long term visit is perfect.
Learn the city, the neighborhoods; visit with other expats, and also locals if you can to start to develop a support network.

Sites like www.expatica.com are fantastic resources, though it does not cover Singapore I think; you should be able to find plenty of sites though.

If you are moving to "get away" from something, then yeah it will follow you. If you are moving because you have a love for exploration and learning new things, even if they are very hard to learn, and to experience life in another culture, then teach those values to your kids and do it !

What do I miss? Not a lot to tell you the truth; I can find everything I need here, including a tight knit group of expat and local friends.
While the idea of going to a local taco shop at 1:00 AM in Austin Texas is something I occasionally crave, it just makes it all the more special when I do get to go home.

And the truth is always, if I really miss it too much, a one way airfare takes me right back.