My experience with Trace Mineral Research was not pleasant. Their supplement caused me more problems than it helped I feel. Go ahead and try it though to see what it does for you. My heart palps only got worse with it.
Have you tried to increase your potassium intake at all? It sounds like your deficient in potassium. Have you had your potassium/sodium level checked?
I use Morton's Salt Substitute. It's potassium choride instead of sodium chloride.
By the way, stop drinking tap water. Get spring water, even if it's just ozarka brand. I also have a shower filter that filters most of the garbage out of the water, which I would highly recommend.