Try shorting the thermistor wires and see if it closes. Thermistor has to be plugged into the ECU.
Don't use a screwdriver to turn the idle motor valve. It's a soft metal and you could damage it. I'm guessing someone already did damage it which would be why it's not closing more. Use something soft like wood.
Also note the idle motor will not close fully with a stock ECU. It will still be about .1" open.