How was the coolant level checked? It is very possible for the reservoir to be showing full and there be air inside the engine’s water jacket. In a properly functioning system, the expanding hot fluid would push past eth radiator cap and into the reservoir and then be drawn back into the engine when the engine cooled, but if you have a leak in the engine itself (such as in the water pump) it could pull air back into the system when it cools as well as pulling coolant back in.
On this engine, the water pump is I believe driven by the the acessory belt (the engine has a timing chain) and if the water pump is leaking it could leak onto the belt driving the AC compressor and cause the AC system to stop working (that compressor belt needs good traction) as well as causing coolant smell, coolant loss, and a path for the engine to draw air into the system when it cools. As a metter of fact, the engine could even be breathing in and out of the leak and the level in the reservoire remain stable.
I think the level in the radiator (ignore the reservoire) needs to be verified, the system needs to be pressure checked and a close look taken at the possible leak places. A dye might even be appropriate.
The good news is that you’ve had the good sense to stop driving when the light illuminates. That probably kept a simple leak from becoming a destroyed engine.
Post back with the reaults of the test. We care.