In a vacuum a 1kg object and a 1000kg ball will accelerate under gravity at exactly the same rate. If they have the same coefficient of restitution then they will bounce with the same velocity as well. What you are seeing is physically correct.
If you want the ball to fall slower you will need to increase its damping rate.
The default damping rate is 0.05 so you will need to experiment with ballDampingRate > 0.05 until it provides the behaviour you want to see. It might be useful to set the angular damping rate to a higher value than the default too. For a more complete model you could also apply forces to mimic aerodynamic drag working against the ball.
To make the building part bounce less you will need to decrease the coefficient of restitution. It is probably a good idea to set the restitution to zero. To do this you need to create another PxMaterial with zero restitution and then apply that material to the ball’s PxShape on construction.