An update:
I went to the independent Subaru shop today and had them look everything over. The tech was of the opinion that nothing is wrong with my car.
There WAS a large amount of coolant down in the left side of the engine. But levels were fine and no leaks visible in the system. Could it still be there from when a hose broke in November? Could spilled coolant in the engine bay send the smell through the vents inside the car?
They also pressure tested everything, visually inspected the whole system, he even went under the dash and poked around and saw none of the usual suspects with a leaky heater core.
All I can do is give the engine bay an extreme cleaning and keep on monitoring coolant levels.
I shouldn't be complaining.
