Coupon Discounts

Hi,

I hope you are all well.

I have a question on Ecart's Discount behaviors
I have been asked to set up a few discount codes for our online ticket store, this is no problem 10% to 25% completed quite easily

The one I'm struggling with setting up is a 'free' family ticket, we don't offer a complete family ticket (we always get asked what constitutes a 2/2 family) so it would be the combination of 2 products, I've set up the code as follows

function WAEC_CHG_Tickets_FamilyTicket() {
$totalDiscount = 0;
if (true && ((sizeof($this->Items) > 0) && ((isset($_SESSION['PromoCode'])?$_SESSION['PromoCode']:"") == "voucher code goes here") && (floatval($this->GetInfo("001-0003", "Quantity")) == 2) && (floatval($this->GetInfo("001-0004", "Quantity")) == 2))) {
$totalDiscount += ($this->TotalColumn("TotalPrice") * 1);//Result
}
return WA_eCart_FormatNumber($totalDiscount, $this->ForceDecimalsC, $this->DecimalPlacesC);
}

I have come across three issues

1) If I add another product from the requirement IE 3 of 001-0004 the discount is removed completely which is not what I want i would want the 3rd ticket to be paid for at full price.
2) If I add another product IE 001-0001 this also has the discount applied, which is wrong this also should be paid for.
3) If I try to checkout with a 0.00 balance I am transferred to the checkout failure page, I do believe you cannot check out on a zero amount..

Plus If they were free tickets would they need to go through PayPal checkout, I would want to record their details but nt sure how this would be achieved

Any help would be greatly appreciated

Thanks

Andy