Coolant leak?

Have the system pressure tested. This will expose any external leaks. If the vehicle is blowing out white smoke from the tail pipe then you have a combustion leak. Just throwing that out there cause you said it smokes.

Reddish orange sounds like coolant. It could be from pretty much anything, hose that is failing, radiator that has a crack, overflow return line and others. The only way to find it would be a visual inspection, looking for the wet areas where it is leaking. The thing with coolant leaks is that depending on what it is you could easily have a catastrophic failure once the engine and coolant are hot. Also the leak will usually leak more when the engine warms up and the coolant expands. The first thing I would do is check the actual coolant level, then use a pressure tester to find the leak. That allows you to apply pressure to a cold cooling system and look for the leak without burning yourself or risking engine damage.

https://www.2carpros.com/articles/radiator-pressure-test

The repairs would depend on what you find as a leak.

The best way is with a pressure tester.
Or
You can bring the engine to temperature so the system is pressurized. Then with good lighting and dental nmirrors of needbe, start your search.

Are there any signs of leakage?

Mixture is 50 50, what does overcooling mean? Getting the heat back, does that mean you have lousy interior heating? Or the engine is running cool? Is the fan running all the time without the compressor on? As long as the thermostat is doing it's job, car should be near normal temps, that's it's purpose.

To TaurusWheel

An engine that runs too cold and fails to reach it normal operating temperature.
A lack of heat in the passenger area is often the first sign that indicates an overcooling problems, but not always.
When the thermostat sticks in its open position. It allow coolan to flow trough the radiator at all the time, causing only cool air in the passenger area.(Overcooling)

Yeah I know, I was trying to get some info as to whether" trying to get the heat back" meant no interior heating, or getting the car running at normal op temps, sometimes I don't read well, or the questions are not framed too well.

To vikadelic

A 50-50 mixture of antifreeze and wayer that 's presurized to about 14 psi won't boil until it reaches a temperature of about 260 degrees.
50-50 % is correct.
Your cap saying "antifreeze only" mean that do not put oil, brake fluid, power steering fluid. BUT antifreeze only and that is 50-50 or according to your book.( 50% antifreeze - 50% plain water)

For the overcooling problem check if the fan is working all the time ( and let me know)
otherwise, remove your thermostat and check it. :)

Have to have a coolant system pressure test to locate the leak, once leak located let me know where is the leak for an estimate to have it fixed