I don't see where you have implemented start and end date.
in the coupon rules, you don't specify a start or end date, and in the recordset that is used to populate the session, the condition is set to look for Live = 1
nothing is setup for looking at a start or end date.
for the validated entries, it will work if you use the Checkout button to submit the form. the validation behavior on the confirm cart page is set to use the CheckoutWizard_submit button as the trigger, no validation will happen on filling in the voucher.