You're english is fine.

1) I don't know about the exact date, if there really is one, but I'd say early to mid 80s.
2) Yes, and there are more and more every day. It's a very under-represented group, and we're constantly trying to attract new women to Parkour. There are quite a few who are REALLY good, too. Offhand, I can think of a Girls-Only Toronto jam video, and a video of few girls from Mexico who are incredible.
3) I find schools work well. Colleges, community college. But truly, you can train anywhere. If it isn't a completely flat parking lot, there's something you can find there.
4) It's somewhat similar to early skateboarding culture. The comparison has been made before. We're definitely trying to NOT head towards current skateboarding culture, which is seems to be based entirely around big moves, sponsorships, and commercialism. (Some would say we're already there, others, including myself, disagree.) It is, like I said in #2, primarily young men. But we also have older men, young and older women, and everyone in between, and we're a very open, accepting, inclusive community.
5) A lot of us are students, just because of the age demographic Parkour tends to lend itself to. I, myself, go to college (was a Computer Science major, now Criminal Justice/CS minor). I have also been a martial artist for about 8 years, I've been running for a while, I rock climb, and I've just started doing gymnastics as well.
6) Everything. The feeling of freedom you get when you walk down the street, glance at something and say to youself "I could get over/through/under that." I love how the skin on my hands has toughened and how it doesn't really get cut up as much anymore. I love the fact that my body is not pretty and well preserved, but hard and rugged, with minor cuts and scraps everywhere. I love the inability to move the next day after a long and hard training session. Most of all, I love the people. At a single jam, I've trained with people coming from all income brackets, all types of families, a wide range of ages, with different nationalities and professions and interests. But Parkour makes us blind to all of that. People I would never meet or hang out with, just because we didn't have anything in common or we had no reason to meet, I have met and become instant friends with. We are not black or white, we are not American or Canadian, we are not rich or poor, students or employees. We are Traceurs.
7) I was talking about this with my roommate, and I told him "I've had a major revelation, been inspired to redouble how hard I train, everytime I meet up with the NYC Traceurs." That entire area is full of people who are so talented and dedicated, everytime I meet with them I see how they train, how they think, and it really inspires me to train (and keep training) harder than before.
Other than that, I'd say a few other defining moments were when I first heard certain quotes. First, when I watched Blane's "Power is Nothing Without Control." That quote has become my personal motto. I have been weaving it into my life, as well as into my parkour training. When I teach Taekwondo, I teach this. When I train Parkour, I teach and practice this philosophy. The other quote is "A bad traceur drills a technique until he gets it right. A good traceur drills a technique until he cannot get it wrong." I don't know who said it, but they are so right.
So... I hope that was good. Any further questions, just let me know.