I'd start by bringing the problem to your dealer unless they have tried and failed to remedy the problem. If they can't help, Jeep Cares is a member on this site. You can send them a PM.
If Tripod is wrong, it could be that something is blocking your defroster from working. Leaves from autumn? Ice in the intake?
I notice that these little engines take awhile to warm up and when its below zero F, if I run my heater on high the engine actually loses temperature. Maybe if you backed the fan down a notch or two the air from the defroster would be warmer and do a better job.
If my windshield is frozen over I'll start my car and put the defroster on the warmest setting and lowest speed. I don't want to hit frozen glass with really hot air. Never happened to me, but I've heard of people cracking their windshields.
I think the reason why it takes so long for the engine to heat up is because of then thermostat/fan settings isnt tuned properly for different ambient temperatures. If you open the coolant temperature tab and watch how the temperature move, you will see it heats up to 120F pretty fast. But that that point, the electronic radiator thermostat partially engages and it starts circulating the coolant from the radiator. Then the coolant temperature stays around 120F for some time until all the cold coolant coming from the radiator is circulated to the engine and heated up to at least 120F. Since the thermostat closes if the coolant temperature falls below 120F and opens the moment it goes above 120F, coolant cant build up any heat until all the coolant within the radiator plus the engine (plus the heater core if heater is on) reaches to at least 120F.
At somewhere around 160F, thermostat is completely open and once you hit 200F, radiator fan engages (I assume fan also has certain settings as it gets loud after ~215F, at some point oil cooler and its fan also turn on). I dont think engine volume has a direct effect on this since larger engines also have more coolant and oil, so overall, they should all heat up similarly. Russian use 1.1 and 1.3 liter Lada Nivas for extended periods of time in Siberia where temperatures are probably way below what we experience here in US.
In older cars, you would need to install different thermostats for winter and summer, just to prevent this issue. But on Compass, for some reason, the thermostat and fan behave almost identically for both summer and winter. Which I think is the reason why it takes so long for the engine to heat up. In my case, engine takes something like ~3 mins to heat up to 120F, but it takes more than 10 mins after that to reach 215F.
I think they should have just made the thermostat open much later if the ambient temperature ,or maybe the oil temperature, is below a certain value. Because in my case, thermostat opens when the oil temperature is still not even registering and it is fully open while oil temperature is half way to optimal (which means there is no reason to start circulating coolant to the radiator).
I also experience the same thing about heater being able to cool the engine
. I think this is also due to thermostat settings since both the heater and the thermostat engages at the same temperature of 120F. So if you turn on the heater, you effectively have two locations that heat exchange the temperature and the oil is simply not warm enough to heat up the returning coolant, especially if you are going down hill.
Another thing to keep an eye on is the fact that once you turn on the defroster, it blows air to the glass, at the temperature you set the HVAC to. So if it is set to 72F, it will blow 72F air to glass. All the previous cars I owned blew "max heating" air to the glass on defroster setting, but compass doesn't do that. So if the outside temperature is too low, 72F (or whatever it is) air might not be able to defrost. So for better performance, you might need to manual set the heater temperature to max after turning on the defroster.
The reason why I suggested OP to check for water leaks is the rear window. I have never heard ice building up from the inside on rear window with resistance wiring. Those wires get pretty hot and I cant see how ice can form unless there is excess amounts of water vapor inside the card.