1 & 2) If you click on User CP, at the bottom it shows you how many points you have, as well as the 5 most recent reputation thingees you received, complete with comments if they left them. They are, however, anonymous.
What I've noticed is that it seems to be weighted. I've had people give me negative reputation, and I lost no points. However I had someone give me two negative reputations and I lost 30 points. Then, after just 3 positive rpeutations, I was back at 53.
So, I still dont know how it's calculated, exactly. I just know that I seem to be stocking up on positive reputation now that the election's over.
Maybe I'll have enough built up to stay in the green through the 2008 campaign.
3) I dont know the levels either, but I think that Kat is the only one I've seen with 3 green dots, and gbg is the only one I've seen with more than one red.