Re: 20 rep squats
I'm personally a fan of 20 rep squats having started doing them after reading "Brawn" probably 10 or 12 years ago. While some of McRobert's stuff is a little off (diet), I like his 20 rep program.
Basically, pick a weight you can do 12 times, but stop after 10. From there just do rest-pause till 20. Nothing mind-blowing, basically what it looks like you're doing. If its a weight you feel like you could've got to 13 reps with no pause - go up.