hi!

I want to switch 2 hydraulic valves at the same time.
The valves using 30V and about 3A.

I'm using a Mosfet from Adafruit
http://www.adafruit.com/datasheets/irlb8721pbf.pdf
for switching a Profet from Infineon
http://at.rs-online.com/web/p/intelligente-leistungsschalter/7528265/

The problem is, that if I'm switching the Profet  OFF, the voltage only 
drops from 30V to about 28,8V not to 0.
So I added a pulldown-resistor at the output of the Profet, but I'm not 
sure about the right amount of Ohm.
If I'm adding a 10k pulldown-resitor I'm getting 0,162V
4,7k pulldown = 0,074V
2,2k pulldown = 0,035V

So my questions are:
x why do I need a pulldown-resistor in this case? (I know why I normally 
use one, but if I think about switching off a normal mosfet, voltage is 
0)

x and  what is the right amount of Ohm for the resistor for switching 
the 3A valves??

I have attached a small graphic of my circuit. Pins 1,2,6,7 of the 
Profet need to be shorted according to the datasheet.

thanks in advance