Given your weight a resting HR of 100 may be normal for you. Do you have another reading you consider normal?
For most, I think a resting HR of 100 while marginally high would not cause many symptoms other than a lack of physical endurance... that is just a little exercise will drive the HR too high.
From what you have posted the only advice I can make is lose weight, I bet 60 pounds off would make a big difference... but you shouldn't stop there.
I am 6' 5" and old, and last year I developed/detected a obstructive sleep apnea problem. I weight between 245 and 250. The Pulmonary Specialist said my throat was narrow and loss of some weight might clear the obstruction. I lost about 20 pounds, I run now between 225 and 230 and I no longer have any apnea symptoms.