I don't mean to come off as harsh, so take me with a pinch of salt, but...
It appears you need to increase your knowledge of Actionscript (again, Read my above sentence). You need to find out how to store values and where to keep them inside facebook, so the player can save the city, this will include storing building locations, population, needs and wants etc.
I'll quickly answer a few questions as roughly and half arsed as i can
1.) I'd set it out into tiles like a chessboard, simple keep the location of the building (also useful for saving the data out) in a grid format, using letter or number values. Ie. City Hospital takes up grid space 12,51, this can be stored and then loading back up if someone comes to visit your town.
2.) Not a feature request, but a request for you. Play Sim City and analyse the hell out of it.
3.) A levelling system in a city based game would have to rely on the state of your city, this means your level would fluctuate though. So if you only unlock certain abilities during a higher level, if your city starts to drop in quality then you will lose those abilities, thus entering the slippery slope of your city becoming a slum.
4.) If you're working on real life time, then just check for the last date the taxes were paid and how long it has been, then increase the players money based on the number of residents.
5.) The first step would be to build a road and have people inhabit the squares around the road. Lets say every hour you run a piece of code that checks for roads and the space around them, if there is space then a new resident comes to build a house. Obviously there will be some sort of randomisation or logic based on the area of town (industrial, business etc) and the state of the city itself but over time people should come to live there.
6.) Use a sim city style radius for schools and public services, if a certain amount of people are out of the radius then increase a bar in your stats and have warnings come up when it reaches a certain level. Have a limit on how many people each service can handle, if there are over, say, 100 people inside the radius for the service then increase it that way. Same with roads. Just say that only 12 people per road square, check for the amount of road squares to the amount of people and increase traffic flow based on how close it is to the limit.
7.) I'm not entirely sure what you mean here, is it the relationship between your citizens? I'd check for population again, if a place is too overcrowded then it will lower the general happiness of the town. Along with how dirty your city is.
8.) Plan, prototype, test, fix, test, move on to the next feature. I have
something on my blog that i wrote in the forums that you might want to take a look at. I really just rant about how i like to do things but it might help with getting a decent plan down.
I would recommend after getting a good plan together that you rapid prototype something in DBPro or another easier language, if not just to test how well features work, or just as a starting point for porting to flash.
Same rules apply for a rubbish around the city, have the garbage dumps only support a certain amount of people and a certain area, when they are overworked, decrease moral of workers, increase the rubbish around the town, decrease city happiness, all based over time.
Like i've said i'm not sure this will be the best way to do this, i'm just thinking out loud.
