gimel has given you excellent thyroid information.
I'd just like to add that insulin is often called "the fat storage hormone". Insulin resistance (pre-diabetes) means that your body is still making insulin, but not using it correctly. Each time you eat something that spikes your blood glucose, your insulin levels also spike in an attempt to reduce the glucose level. Whatever glucose isn't used for immediate energy, is then stored as fat in your body, waiting to be used for energy in the future. It rarely is, which causes us to gain weight.
Insulin resistance can, often, be treated simply by changing the diet - instead of eating things that spike the blood glucose (in turn spiking insulin), like white bread products, pasta, rice, sugar, etc - called simple carbs - we need to eat things that will keep blood sugar levels more stable. If we don't spike blood sugar levels, we won't spike insulin levels, so there won't be excess insulin to shuttle that glucose into fat cells.
The Mediterranean diet has been determined to be one of the best for insulin resistance because it focuses on vegetables, whole grains, lean meats/fish and "healthful" fats, like coconut and olive oils.
You are not on the right dose, or right med. Hypothyroid patients taking only T4 med often find that they cannot get their Free T3 high enough, even with excessive levels of Free T4. The T4 med is not being converted to Free T3 which is the biologically active thyroid hormone used by all the cells of your body. Your Free T4 is over range, which is the likely cause for the symptoms you mentioned: fast heartbeat and inability to sleep and anxiousness… Everyone is different in their thyroid needs, but for most people o relieve hypo symptoms requires Free T4 around the middle of its range, and Free T3 in the upper half of its range, and increased from there as needed to relieve symptoms. Also note that you should always delay your morning dose of thyroid med until after the blood draw, in order to avoid false high results.
So you actually need to get your T4 dose reduced, and add some T3 med to your med. If you want to see just how important Free T3 is, click on the following link and then scroll down and click on Fig. 1C. If shows the average result from 3 different levels of Free T3, expressed in pmol/L.
Hypo patients are also frequently deficient in Vitamin D B12 and ferritin. D should be at least 50 ng/ml. B12 in the upper part of its range, and ferritin at least 100. If not tested for those you should make it a priority and then supplement as needed to optimize.
You mentioned other symptoms that seem to relate to the high insulin level. You can get a lot of good info from this link.
A good thyroid doctor will test and treat a hypo patient as needed to relieve hypo symptoms., rather than just based on test results. You cannot go to the Cleveland Clinic and expect to automatically find a good thyroid doctor. Most doctors are like the Endo you already have seen enough. They only pay attention to TSH. If you don't know of a good thyroid doctor perhaps we can suggest one in your general area, that has been recommended by other hypothyroid patients.