In response to 3- lower that seat!
In response to 8- no it is not a good idea. i run my tires at 20 psi.
Trying to remember back to my first few months, and the tips that I found useful....
1- Use one (maybe two) fingers to brake.
2- Skills such as wheelies and bunny hopping actually have uses
3- Don't grip too hard on descents lol