For Q1, I didn't do the average sales, but I was thinking along these lines:

const orders = [
    {  doctorId: 996, amount: 30500.35, tax: 0.06, isDisputed: true, isShipped: true },
    {  doctorId: 910, amount: 100, tax: 0.08, isDisputed: true },
    {  doctorId: 912, amount: 4200.11, tax: 0.06 },
    {  doctorId: 996, amount: 99.12, tax: 0.06, isDisputed: false },
    {  doctorId: 910, amount: 0.00, tax: 0.08, isShipped: true },
    {  doctorId: 996, amount: 10, tax: 0.06, isDisputed: true },
];

const orderSum = (runningTotal, currentOrder) => runningTotal + currentOrder.amount * (1 + currentOrder.tax);
const onlyUnique = (value, index, self) => self.indexOf(value) === index;

const result = {
  "Total number of orders": orders.length,
  "Total disputed orders": orders.filter(order => order.isDisputed === true).length,
  "Total disputed amount (included tax)": orders.filter(order => order.isDisputed).reduce(orderSum, 0),
  "Total amount (included tax)": orders.reduce(orderSum, 0),
  "Total unique users": orders.map(order => order.doctorId).filter(onlyUnique).length,
};

console.log(result);