I don't want you to think that I don't believe what you are saying, but I was waitlisted for almost 3 months (early-November through last week!) for just 4/20. AND I was waitlisted for two months (October - November) for 4/21 - 4/25, so I find it hard to comprehend why someone at Member Services would tell you on Saturady that there was availability for this time period. I understand that cancellations happen, which is why I had my waitlist dreams fulfilled, but this week has been booked solid for months!
I'm sorry that you are in a bind, and I know this doesn't really help now, but I would recommend in the future actually making the DVC reservation BEFORE booking airfare. The entire concept of "availability" with DVC is a joke in my opinion. I have lost an "available" room while checking other dates/resorts! Unless I am ready to book that very minute, I pay no attention to what Member Services says about "availability."
The only advice I have at this point is get on a waitlist ASAP and cross your fingers!
Blahnde