In my situation the fluid was actually leaking outside the car but directly in front of the fresh air intake so the odor and steam was drawn into the cabin.

Yeah it sounds as though your core may have failed and I offered my circumstance as an example of checking every thing you can as thoroughly as you can before plunging into the deep end. I had removed my center console and most of the under dash panels and was set to start removing the dash when I got side tracked and accidently discovered the true problem and luckily avoided ripping every thing apart only to find nothing wrong with the heater core. You should be able to see any leaking coolant coming out of the heater box drain that is probably up above the tranny in the hump to verify a heater core leak, the pressure test in-place sounds like a good strategy at this point, good luck!