Chances are, you have a leak somewhere. You can check your hoses and cooling system components for leaks, and repair them as needed. You can either do a visual inspection, or do the dye and blacklight test.
You may also not be changing your coolant out often enough. In the cooling cycle, coolant will change from liquid to vapor and back, with the inevitable result being that some of it will evaporate over time. Coolant doesn't last forever - it does burn out over time, and will need replacement.
head gasket failing
No, you run the risk of destroying the motor.
Run a pressure test on it.
After coolant is added run vehicle to normal operating temperature and re-check coolant level
It can run but if it is leaking coolant it will cause a problem soon.
No , if you start the engine than the oil and coolant will mix and it will also be in the oil filter
I think you would know if you needed a freeze out plug for you would be losing coolant & losing coolant would make your ride run hot.
No, it does not make the car run better. Dex-cool is a type of engine coolant most commonly used in GM products.
Car engines get hot to run generally but if you mean over heated it means that your coolant level is low and you could go buy coolant or you could just fill it with water
Depending where it is cracked, yes. A cracked head can also simulate an overheated engine by pushing coolant out of the coolant reservoir.
Possibly the Head Gasket is blown.
If it's mixing coolant with the motor oil, not for long.