RE: COOLANT LEAK VS HEATER CORE
Get under the truck, if possible.
If the coolant leak is comming out of a small (1/2" diameter) hose on the lower passenger side of the firewall, it's the heater core.
Everything you have mentioned in your posts about this problem points to a heater core.
Looks like coolant, smells like coolant, it's comming from the ductwork?
Only one way for coolant to get into the vehicle's ductwork. Wanna guess how?