When you say the volume of air is limited, are you saying that the fan is not blowing the same quantity of air as it did at the start, or are you saying that the air temp is not the same? I cannot see that the air blower would change speed or decrease in operation, but could see that the air temperature could change, which might indicate that it needs recharging. As for the pool of water under the car once stopped, this is ok, and is normal for vehicles fitted with A/C.