Coolant being pushed out of reservoir

The fan shroud is the thing that surrounds the fan.
The heat is going away because of the overheating and thus air in the heater core.
Fix the overheating and you will fix the no heat.
This cannot be that difficult to bleed the air out of, which leads me to believe that maybe that isn't what is going on here.
Are you allowing the engine to warm up and thermostat open up, then before taking it out for a test drive, double check the coolant level in the reservoir?
This time, do not even take it out for a test drive, once the engine is warm just let it sit there and idle for ten minutes and let me know if it overheats just sitting there idling.
If not, then turn on the AC, leave the blower off, then let me know if it begins to overheat with the AC on just sitting there idling.

Okay, that is fine.