Hyperthyroid can cause extrasystola-s as in your case palpitations (extra beats). Therefore, you should check your thyroid through hormonal
levels and scintigraphy
With regards to MR, the cardiac echo has already diagnosed its presence. According to your saying it is mild regurgitation, which is not supposed to give troubles.
In most cases, it is a hereditary pathology, and the majority of patients know its existence accidentally.
The most important thing in your case is to stabilize your thyroid to prevent further damages to your heart which can aggravate your MR.
Do not worry about your life expectancy. As long as you are taking the right steps, you will be ok.
All the best!