Agree that the left foot should only be used to operate the clutch on a manual transmission, but disagree with the rest of your advice.
Following your advice, if your foot were to slip off the pedal under braking (perhaps if you hit a pothole), the car will have no engine braking effect to keep it under control and you'll most likely hit whatever you were braking for, or overshoot your corner. The shift down or to neutral should come when you've lost most of your speed (obviously depends on how high your gear is), or when you're about to accelerate again.
Similarly, when starting off, releasing the handbrake (aka emergency brake) before setting the clutch will result in you rolling forward or backwards if you are stopped on a slope, or even jumping forward if you panic and overshoot the bite point. Unless you're on the flat (typically in standing traffic), always find the bite point before releasing the handbrake.