Just skip the temperature reading, it doesn't tell you anything anyway (which is also evident from you readings). Just go by the rpm and how well it holds the rpm and needle settings. The 14x4 sounds like a good match based on your rpm numbers. I don't understand why there would be anything wrong with the 10% fuel, or why you did all the testing on the 10% fuel and then flew with 0%?

Some engines actually run colder with a bit of nitro in the fuel, but they also need to have the correct prop.