Hi there,
I think you can achieve what you want with this:
<?php
if($this->config->get('price_with_tax')){
echo $this->currencyHelper->format($this->order->order_subtotal,$this->order->order_currency_id);
}else{
echo $this->currencyHelper->format($this->order->order_subtotal_no_vat,$this->order->order_currency_id);
} ?>
This code is used in the invoice view to display the full price of the order.
According to what you would like to see, you can multiply it by 0.4 to have the amount paid and by 0.6 to have the amount to pay. So you can copy this code in your customized part and give it the form you want
.