Some minor updates ....
Since draining the radiator and replacing the tstat, the mysteriously rising and falling coolant level issue has not returned. Perhaps there was indeed a stubborn air pocket somewhere in the system before.
Regarding temps, they are more steady and peak about 2F lower with the Stant SuperStat vs the Motorad that I pulled out. However, the truck continues to run hot in traffic and when the engine is under additional load (e.g. climbing a hill). Still no overheating.
My Blackstone coolant report came back and supports my findings on the combustion leak test. No hyrdrocarbons detected in the coolant at all. The oil got temporarily lost by USPS and arrived a day after the coolant, so I am still awaiting results on that.
Additional comment from Blackstone Senior Analyst:
No hydrocarbons (oil/fuel) showed up in
this sample -- when that sort of contaminant is
present we'll run a spectral exam to show what
was present in the oil/fuel. There was no such
contaminant to analyze with the spectrometer,
hence the reason for no data being included in that portion of the report.