I wasn't up at the top of Echo, but as far as I could tell, after the press, it was first come, first serve. I don't really know how it effected the rest of the park, but I would guess there were upwards of 3000 people down there, so it was probably pretty sparse on park.
The helicopters didn't actually fly over the park proper, but skirted it to the east. I imagine that people might have been able to see them from some locations though. And no, Wallenda had no safety cable. That's why they didn't hoover right over the ampitheater. If he had fallen, he would have gone down in the trees, out of view of guests. Still, I hate to think about that. Thank God, it didn't happen.