My wife suffer arthritis problem.

Yes, blood donation is good for health. Some studies have shown a decrease in Cancer risk, as well as decrease in the damage to the liver and pancreas in the long run. One should definately donate blood, ofcourse after the entire pre-requisites are cleared.

Did you mean renal ‘collapse’?

Yes, stress can cause heart palpitations because when you are stressed, your body releases a hormone called adrenaline which makes your heart beat faster. But, it could be something else too like too much caffeine or alcohol, certain medications, asthma inhalers, dehydration and other health issues.....