1) Does it sound like a loud "piak" or "tik" sound? Happens mostly on hotter days for me, hardly hear that during night driving or colder days. Maybe something or the screen is not adhering correctly. I just live with it, because mine happen in random, hard to replicate. So won't consult SC on this for now.
2) Is it the absorber sound?
3) The springs are tight. If want to adjust, put a bit of force when resting your back to the seat, then only pull the lever. The action will be smoother that way.
4) If you heavy foot alot and like 4k rpm and above, hard driving highway, your fuel consumption will be high, cannot run away from that. With 2 bars left, you can travel another 50km without worries. The fuel tank is 50L. This car's engine also don't like crawling and idling, drink a lot of fuel during that. Don't compare with vios/myvi/city/almera, these cars are lighter and smaller engine capacity. It is known that direct injected engines don't cope very well with mild engine loads.
5) For me, I would say no harm trying. The paint formula is known in the paint market and can formulate to factory specifications. The part you have to be concerned is the application part, follow carefully then should be ok. Just don't expect perfect finish like the paint shops sifus. If too deep scratch or big patch, cannot rescue....
Did you use soap? And is your cloth genuine mircofibre? If you just want to quick wipedown without soap, it can only be done with very light dust. But for our climate and dusty environment, better soap and wash la....
I din use soap, just plain running plain water. Let the water flow slowly and wash.