By far and away the most important item for optimal cooling is jacket fit. With a Fast Ferment, the jacket needs to be snug without any gaps in the insulation (video link here). If there is a gap, you generally won't notice any performance degradation until your around 15° F below ambient, at which point your cooling speed will hit a wall. So if the system is cooling at 1° per hour then all the sudden you get zero change, it is a jacket installation problem. Even if you think you got all the seams, it may be worth it to take the jacket off the fermenter and give it another go.
The heat sink fin temperature should be about 20° above ambient measured with a laser thermometer. It won't feel hot to the touch, but slightly warm. The rod should feel slightly cool if it's in a body of water. It won't be cold as its job is to transport the heat out of your water/beer and up to the heat sink, but it should be slightly cooler than the water itself. If you remove the rod from the water and let it sit out for 30 minutes while the system is still cooling, you should notice it get very cold as the convection current that drives the heat exchange in liquid is no longer present when the rod is exposed to air, and ice should form on the rod.
Give the jacket reinstall a go and let us know how it goes.