Try the Dibb site which is the font of all knowledge anything Mouse shaped or use the DLP contact us page https://my-disneyland.disneylandparis.co.uk/contact-us.html
As you say its not easy as they have so many offers
We booked our tickets with travel Republic and they were valid for one year from date of purchase,a bit cheaper than paying on the gate,also parked at Disney village which is a lot less busy than the normal car park and less queues to get in.