For better or worse, if you are beyond your rescission period, DVD is probably not going to void and re-write a contract. However, maybe that's for the better, because....
...this sort of thing happens all the time! But, there are reasons you bought 200 AKV points, and all of those reasons are still there. You'll still have years of great vacations and memories.
In particular, there's probably a reason you bought 200 points rather than 300 points. Partly, it was probably because of the $10pp developer credit, which is a nice thing. But, maybe it was also partly because 200 points was plenty for what you need right now---otherwise, you'd've bought more. Sounds like the promotion would have encouraged you to over-buy for what you need right now so maybe it is better that you bought when you did?
Very doubtful. I suspect that if they re-write this for you it would be an exception---and this is the sort of exception that happens at best vanishingly rarely. It can't hurt to ask, but I'd encourage you to expect no for an answer.