Overheating with no heat

I have a 2010 Chevy Aveo LS it has 76k miles on it. My car overheated and the check engine light came on and the code read Low Coolant, when it cooled down I checked it and there is this black sludge in it, but my oil was changed about 75 miles before this and is a beautiful gold. There is no coolant in my oil not on the dipstick, and not after I drained it to check. I have no white smoke or bad odor coming out the exhaust. Before I drained the oil it was drivable for about a mile before it would overheat. I tried a gasket sealant thing my friend recommended and let it idle for 40 minutes to run it through and that is when I realized I have no heat now. I don't know what the liquid in my coolant reservoir is, and I don't know why my heat doesn't work, and I don't know what to do from here.

A little background, a few months my car was overheating and I replaced the thermostat, water pump, the cracked radiator hose, my spark plugs, and the ignition intake coils. The thermostat has been replaced twice in the past year.

If someone could please guide me on what to check so I can narrow down this problem and fix my car it would be greatly appreciated. Thank you!