Adding Extra Customer Email In Woocommerce Checkout

Question

This solution seems to be very close to what you need. But can’t say duplicated as you will need to do some coding to get 2nd email address.
Check out.

Adding a second email address to a completed order in WooCommerce

To get email field from checkout try

get_post_meta( $order_id, '_custom_field', true );

now you might want to get $order_id

add_action ('woocommerce_thankyou', 'myfunction');
function myfunction($order_id) {
  $order = new WC_Order($order_id);
  print $order_id.', '.$order->get_total();
}

Hopefully this will take you in right direction.