Welcome to the forum
The clutch judder is pretty common, my wife's 1.2 Modus (Clio based) has been doing that for a number of years now. You'll get used to it, and find a way to drive around it
First gear is not a synchro mesh, so changing down it will sound different to the other gears. Of course I can't hear it so that is a bit of an assumption on my part.
I wouldn't worry too much about the air intake pipe, replace it when you can, but it won't cause you any major problems.
You may have a bubble in the hydraulics that has caused the change in feel on the brakes, but of course adding a lot more weight to the car will change the way it slows down. I would suggest getting the brakes bleed again to make sure.
Your idle speed and stalling are probably related. It's probably worth cleaning the
sensor, but also worth having a look at the electrical loom where it enters the
. There is a clamp around the loom that has been known to chaff through the insulation causing random electrical problems.
Not sure about the power steering, do you think its speed related?