Hurri6
If I'm correct, one of the questions you have is regarding the increased dynamic pressure at a higher speed?
Remember that total pressure is measured by bringing the air to rest - it is dynamic + static pressure. The dynamic pressure is so high because the air has lots of energy; it's this that is being measured (think molecules pushing against a piston). That's why it is do high in the case you quote.
On another point, even though the speed of sound is temperature dependent, we don't need it to work out Mach number. Both dynamic and static pressures are local ambient - that's the body of fluid you're in at the time of measuring.
Problems arise in the real world because measuring absolute static pressure accurately is very hard, especially with all those pesky shock waves knocking around...
I hope this helps and has not merely insulted your intelligence.