Dysregulation of your heart rate to the extent you're describing is unusual for an mTBI in my opinion. Depending on the dose of Propranolol you are taking, abruptly stopping this medication will result in a reflex elevated heart rate for possibly several days. If you are young and cardiac healthy, there should not be a concern. If there is an underlying problem causing an elevated heart rate to begin with, I would suggest you at least consider other causes than mTBI related. To consider...
Rule out hyperthyroidism....check serum TSH
Rule out a primary cardiac rhythm anomaly... ECG+/- Holter moniter
Rule out anemia...Hemoglobin
Rule out (much rarer) pheochromocytoma....24 hour urine for metanephrines
Just some suggestions...hope it helps

PS Nortryptiline can cause excessive sweating but you are on a low dose. Just have your pharmacist check that there are no drug interactions with your other meds that may cause the Nortryptiline levels to rise.

PPS If you are taking regular amounts of pain medications as you listed, the caffeine content can increase heart rate