Unfortunately, no, you will not be able to. The codes provided are valid for new bookings only.
Try double-checking that the options you've selected for your vacation package, like the destination of the hotel. The discount code field will only appear when the options you've selected are eligible for the discount.
The base package price of a vacation is the cost represented in the "Flights, hotel and extras" section of your price summary, which you can find on the left while you are booking. Your discount will be applied to this portion of the total cost of your vacation package. Discounts cannot be applied to taxes and fees, which are represented separately in the price summary section.
No. The discount is applied per booking, not per person.
No, codes that are specified for vacation packages cannot be used for flight-only bookings.
No, currently you cannot use WestJet dollars in combination with a vacation package discount code.
After pasting in your code on the payment step, you will see a message stating "The promo code has been successfully applied. You saved:" followed by the discount amount that was applied to your booking. You will also see the discount applied in the price summary at the left of the screen while booking.
The discount code expiry date will be given on the offer landing page. It's generally at 11:59 p.m. MT on the given end date unless stated otherwise.
Blackout dates are specific to the offer for each discount code. Refer to the individual discount code details to confirm whether it has blackout dates.