I don't know how many liters are expected when replacing the pan. In the range of 3-4 sounds right, as about 8 liters is typical for the entire transmission, and half that is in the torque converter.

Half a liter isn't going to make the difference between moving and not moving. You really need to check the fluid level in the pan - at least make sure there is _something_ in there. Note the clutches in this trans use graphite, so the fluid turns dark as they wear. Probably inky black on a 150K mile car. This is just normal wear, so don't be too alarmed if the fluid is not all pink and happy looking.