Eh I stumbled upon this site, and I was bored so I figured I would clear up some stuff.
The video you posted is on Auto Play (please note the big Auto Play at the bottom of the screen). On the other hand this song is not impossible at all, I have passed it as have many others on Stepmania. People have actually gone on to play the song on 1.3x Rate where the song is actually sped up 1.3x faster.
search on youtube dossar 960 bpm 1.3
In terms of the fastest on feet, that would probably be MadMatt currently, this is probably his most impressive feat, but you should check out his channel for more. His footspeed compilation videos are very impressive.
Seach Mad Matt Extratone Pirates, or search Mad Matt Footspeed
apparently I can't post youtube links until 15 posts...oh well.
