I would drop your squat sets down to 3 sets of 8-10.
The "1 set of 20" is a breathing set. Meaning, you choose a weight you can do about 10 reps nonstop with. Then you rest the weight on the floor, DO NOT take your hands off the bar, take a couple of breaths (no more than a 3 second rest) and grind out 1-3 more reps. Repeat until you hit 20. NEVER compromise form!!! If your form suffers, lighten the weight.
The workout should take you around an hour.
INTENSITY is the key for this routine. Each working set leaves me drained, somewhat light headed from the exertion, and breathing heavy. Rest no more than 2-3 minutes between working sets. Have a spotter if at all possible. Never risk your safety.