Maybe I missed it but the one thing I don't see in this is what the temp of the creme brulee was when you stopped cooking. The egg yolks set between 149°F-158°F (65°C-70°C).
Looking at the photos, I suggest insulating your vessel. I use a silicon trivet under and a towel wrapped around mine.
An accurate thermometer (Thermapen) is an important tool both to make sure that your cooker and your recipe are going to work.
Usually I put my food in when I turn the cooker on and let the food come to temp with the water. I haven't cooked anything in an open container, I always bag it, so I don't know if evaporation is an issue but I doubt it.