Here's the latest finding.

Wife got home from work, I noticed a small puddle starting to form under the AC firewall overflow which I've 100% seen antifreeze come out from. I popped the hood, the coolant overflow bottle was boiling from a 1 mile drive home from work. Also I waited ten mins and I then took off the radiator cap, the radiator was mostly empty. There is no leak in the radiator, only thing leaking was that a/c firewall overflow. Is it possible the radiator forced all the antifreeze into the overflow bottle because the thermostat was stuck open? Does this sound like a thermostat issue or still a heater core problem do to the leak from the AC box overflow tube. I have noticed the passenger floor is wet, but I do not get a smell of antifreeze. I also used a paper towel to see what color the water under the floor mat was, and it was clear maybe just over perspiration? The hummer does not smoke, the transmission fluid is clean n does not smell burned or anything added to the fluid, also I had found that there was a coffee/mocha colored layer of film under the oil cap when I went to check the oil. But I do remember that being there for sometime (possibly the last 2 years.) I would clean it off and at oil change time & it would be there again at the next oil change. Maybe that's a clue for you guys maybe that's something totally different. I'm so nervous its the heater core but I'm so hesitant on bringing it in and it not being the real issue.

Thanks again for all the help so far, hopefully with the added information I have given you guys you can determine what the issue is better now.
I really appreciate all your time on this
Jeff

 

check to see if your engine oil level is rising. the coolant might be going there. if it has overheated it might have cracked a head or blown a head gasket. they sell kits to test for exhaust in the coolant. here is a video of some one using a test kit but that kit wont show if the oil and coolant are mixing directly like in a radiator

 

When the T Stat is stuck open, your engine will run too cool and take a long time (10-15 minutes depending upon load and outside temps) to reach full operating temp and will throw a CEL P0128, rule that out because it would not be boiling in a mile or so.

If you have a heater core leak, it must be a good one. Re-fill with 50-50 coolant water, start the truck on a level surface and let it run looking for it to start leaking coolant onto the ground. If it makes a puddle, from your HVAC drain that is red, you found your problem.