Sorry Erik but it’s just that brush hanging on the wall, I keep getting this picture of you sitting in that box getting your back scrubbed!
On a more sober note and notwithstanding the comment about the colour and smell of the water found in the exhaust, could it not be a combustion product? Maybe the hint lies in the name, Hydrocarbon, burn a gallon of petrol (4.45 litres) and among the other products of combustion you get about 10 pints (5.7litres) of water.
Referring to the pressure test, very ingenious but I doubt that you got more than a couple or three pounds of pressure in that unsupported inner tube. More pressure might reveal something but probably not and after all it is not a pressurised system.
