You need to use attributes to achieve these things. Have you used them before?
Booleans will let you simply check if the paddle has been hit.
So when the ball hits the paddle, set it to true, when it hits a brick or a wall, set it to false.
If the boolean is true when it hits the powerup, run the code that triggers the powerup, if it's false, ignore it.
For the 8 second slow down, you'll need to store the velocity in an attribute so that you can refer to it later and make the ball slow down. Then every 8 seconds you would set the velocity to 'current velocity - amount (the amount to want to slow down by)'
To reset this, simple put a line in your existing code that adjusts the score to reset the velocity.