With regard to the idle temperature, that's typically not a radiator problem unless it's in real bad shape. Disconnect the AC input to the controller, temporarily connect it to 12V, and let the car idle. Once it gets to temperature, touch the drivers side tank, it’ll probably be cold. If it is, the thermostat is still closed. If the temperature at this point reads higher than the thermostat rating, it’s either a gauge or thermostat problem. If it’s hot, as well as the air coming out of the fan, it’s probably a head gasket or tuning problem, if the tank is hot, but the air is cool, it’s a radiator problem
With regard to the freeway driving, it could be the radiator, but if you’re missing the lower air dam, which is often the case, it’ll also overheat at higher speeds. The clutch fan will flow about 7,000 cfm @ 3,000 rpm and will cool the car without the air dam, while even the m8 electric fan won’t