Better your hearing than your life.....not all the noise comes from the end of the barrel, you would still incur hearing damage as you describe.
Windshield will not fracture to the point of not being able to see. They were demonstrating it on 'Personal Defense' on the Sportsman channel a couple of weeks ago.
Depends upon circumstances. if there was somebody pointing a gun at me, with evident intention to fire, then, yes, shoot back first.
If it's somebody with a baseball bat, then you have a better blunt weapon, floor the gas.