It's not a zero sum game. If someone is unemployed, they become employed and create some goods or services, they both can spend more money and the business can sell it for more money than they pay out as salary
So you have created wealth that didn't exist before. It is possible for everyone to be rich, provided we automate enough tasks that nobody is wasting time on menial labor
The government lowers interest rates to increase economic growth and when the inflation is low. Lending increases the money supply because banks are not required to have full reserves. So yes, the Fed actually increases the effective money supply at the correct rate depending on whether they want the economy to grow or to control inflation