Spacebars have the same amount of throw as any key on your keyboard. Additionally, the force required to press the spacebar is less than other keys because the keycap for the spacebar is heavier.
Oh, not on my HP. Any of the arrow keys (specifically in this case the up key) has way less push to it than the spacebar.
Depends on if you are using a dell quietkey or a macbook pro.
No, not really. Also, no other key suffers from not being pressed from the center of the key.