1) Generally, only major, traditional holidays are celebrated by a community. I.e. not much of that Chinese Communist "Unification" week celebrations going on last week on the mainland. In America, we usually invite each other into our houses. The parents talk about their kids disrespecting their culture while the kids do a mixture of playing video games or surfing the TV, with those bringing their own games being surrounded by followers.
2) For New Years, most still try to make time to watch the official Festival. It is like the American New Years show, except there are a lot more Joke-skits, American Idol Judged-style mass performances, and propaganda. I remember in New York and, lately, in Cleveland the Chinese make a traditional parade down the main street of "Asian/Chinese Town" with the lions, wushu dancers and stuff. As for Mid Autumn, it is a lesser version of New Years except we all buy each other boxes of expensive mooncakes while apologizing for accepting expensive mooncakes from our friends. I am not very well aqainted with Qingming Jie, although it probably came up in some reason or another for visiting or hosting parties.
3) Generally, most of us (As in parents and those who were brought up to at lest 3 without fast food) consider restaurant food "Americanized" and would eat them, but while constantly (sometimes silently, you can see it in their eyes) complaining about how it tastes wrong. However, if it gets dressed as a buffet, or Asian in general, they don't care. As for those who do cook at home, it is a mix of traditional stuff they try to remember, and the same stuff from the restaurant except "it's cooked right now".
Mooncake-Doughy rice outer covering with firm filling. Contrasting with hard, glazed ones with really soft filling. Generally eaten sliced.
juehua tea- Not Sure. If you are talking about the tea with flowers (never really figured out which flowers are in there) then yes, it's here.
rou-gan- Yea, not surea bout this one.
Shark Fin- Nope. I can't find that even when looking at the hard-core section of the chinese grocers my Parents go to every month or so. We have to drive between 30min-hour depending on conditions.
steamed dumplings- My parents make them, some dimsum has them, but most make the less tempermental potsticklers. I love the soup
3) Like me, the 'community' comes from all over China. It's more of a loose connection where Parents constantly get invited to meet new friends while slowly forgetting old ones, while the kids get used to just calling each other "Hey" when they first meet, since they don't know how often they will get to see each other.
4) Yup, according to my Mom and the Fascist-Chinese Kids, the use of chopsticks show a superior mind.

Yes, Rice is served nearly every day. Although it isn't boring because the dishes (and their sauce!) is different. The sauce is really important in the flavor of steamed rice.
Hongbaos have turned into excuses for kids to ask for a third present holiday (birthday+christmas+chinese new years) while parents just calculates the dollar amount from the grades of the kid in question; which is usually very high.
As for Oral Traditions, generally the Parents try to get us young with poems and stuff, and tell about the different histories of china. 12-years of Euro-centric education really does leach that out of you, although I can probably understand most of the "4-word Proverbs" being thrown around the adult table. Not that I really want to hear what they are talking about after sedating us kids with videogames, movies, and companionship.