Hi: I am having a similar problem.
I am not overweight, don't have high blood pressure never have indulged on sweets or carbs and started having
ringing in my ears. I noticed that they ring when I eat carbs or don't eat meat protein. I had 1 reading of
105 glucose fasting and insulin 8.
I have not done the glucose tolerance test because my next test indicated that my glucose had gone down to 87 fasting.

However, I had a heavy metal test done and it indicated that I have more than twice the amount of mercury expected for a person to have. I also have lead but not as much...

Tips to control the ringing in my ears or insulin resistance.

Eat 1 egg for breakfast and vegies, eat chicken and vegies for lunch
eat a small portion of meat protein at night and vegies.
no fruit no pastas no sweets and no grains.
Never skip meals and eat small portions.
I am starting to take out the mercury. I also came to the same conclusion as you. I had 2 challenge tests to see which chelator worked better for me. I am waiting for results.
I also have circulation and memory problems and hair loss!