function getFormData(selector) {
  const form = document.querySelector(selector)
  const price = form.querySelector('b')
  const location = form.querySelector('i a')
  
  const [sum, currency] = price.innerText.split(' ')
  const address = location.innerText
  
  return {
    address,
    amount: {
      sum: +sum,
      currency,
    }
  };
}

const data = getFormData('#invoice_form')

console.log(data);

{
    "address": 4279380040001111,
    "amount": {
        "sum": 1000,
        "currency": "rub"
    }
}