1) Not many, maybe 5? When I used to do them regularly I could manage around 40-50 max. But I rarely do them now. Reminds me I should do a few more really!
2) No idea. I usually do normal squats in sets of 10, like 3 x 10 with a 30 sec pause between sets. Sometimes loaded with a small kettlebell. But I reckon I could do quite a lot if I tried.
3) I can ride 100 miles over mountainous terrain at tempo with a good few threshold efforts thrown in (I would bet good money that the guy in your video would not be a good endurance cyclist, simply because he's carrying far too much upper body bulk)

Fitness comes in all sorts of different flavours. Pro marathon runners are fit and so are pro heavyweight boxers and cross-fitters. But they all have very different strengths and weaknesses. Pro road racing cyclists have amazing aerobic fitness, endurance and powers of recovery. Totally off the charts at World Tour level.