Anti freeze won't carry off as much heat as water in the chemistry lab, but I have not seen that much difference in practice. If the temps go up and never stabilize, I really don't think I would spend much time going down that bunny hole.
Do you know if your fan is turning on and off per the switch settings (assuming it is switched on and off with a thermistor switch and relay)??
It should cool better when moving than sitting still, unless the fan and shroud block airflow when moving, and the fan is not coming on. If that makes sense.
Have you bled the system to make sure you don't have an air pocket that is preventing the water pump from moving water through the motor? I would guess your radiator cap is the highest point of the cooling system, take it off and while the motor is running, fill it full, let it run, fill it full, squeeze the top radiator hose and make sure you feel water running through it and that it gets hot....
