I'm not sure I understand.. I realize it is hard to explain the situation. But it seems you're not enjoying what's going on so there must be something wrong!
You don't need to brake except for slowing down; pressing the brakes should help the shifting down. It shouldn't be causing vibrations, engine cutoff or revs. What do you mean, revs? Do you mean it is like the clutch is released completely for a moment?
However, this is a manual gearbox - shifting from 2nd to 1st gear will give a massive jolt unless timed perfectly! In normal driving, you never really shift down, let the computer do it for you.
It is an astronomical wild guess, but (as you said in other topic) your clutch position is calibrated, but the sensor is wrong.
Maybe make a youtube video of the situation?