The back up at DL is DLH or PP hotels or booking offsite. The DLH or PP cost a bit more in points but there isn't a $95 exchange fee and the rule of 4 does not apply. I'd suggest waiting to see if your waitlist fills. (I almost waitlisted the exact same thing yesterday. Heard the exact same thing you were told and seriously considered calling this morning to book the 5th & 6th but I am not the one who snatched them away!

). Then if it's getting closer and it hasn't filled you can book DLH or PP. I would wait though b/c once you book one of those locations your points become reservation points and can no longer be used for a
DVC room.
As far as the waitlist filling it's normally only if the days for the full time become available. DVC stopped the day by day waitlisting and the only way to do that is to call back periodically and hope to catch any single days that have opened up.