Hit Location
You should use Hit Location as place to play sound at 
Vector Length for Correct Calculations
You definitely are not going to get consistent results measuring whether each component of vector is > than a positive large number,
you should use vector length
vector length returns positive size of vector, whereas components could be legitimately negative
You might want to use Print Message to find out what sort of impulse values you get with this method.
Here’s a pic for you!
PS: regarding hit event, which parts do you want more info about?