Docrio, it sounds like you are in great shape. I wouldn’t sweat the thermometer. The other measures (sleep, wellbeing, hormones balanced) are more important, and you are likely to just mess up your body searching for ways to get to the “perfect” temp. Just keep doing what you’re doing now and enjoy life.
You had a really great reaction to eating for heat. A 3-pound gain over a 3-week period puts you in an enviable category. Just out of curiosity, did you come from a background of dieting? How are you approaching eating for heat? Maybe some others here can learn from your success.