The electric shock sensation in running water is, I hate to say it, almost certainly badly earthed electrical connections. A lot of electric showers, water heaters, and just plain old ancient household wiring can have degraded or non-existent grounding which can lead to a persistent tingle on the skin or other extremities which are in contact with the water. If this is a rapid twitching / pulsating feeling it's almost certainly down to mains AC supply: you don't need a cardiologist for this symptom, you need an electrician.
Your resting heart rate sounds good, and the quick drop to below 100 after hard exercise sounds good too. But I'm not a doctor or health professional, so that's just my thoughts about it.
Your exercise tolerance sounds good.
The left side stomach feelings with some bloating could be acid reflux irritating the esophagus, and/or tummy issue?