Actually, the points will not be usable for any non-DVC Disney hotels at WDW since resale points are excluded from that option.. Moreover, even a DVC owner not subject to the resale rule could not make a reservation after July 31, 2021. Though a member can reserve a hotel room to stay for times that occur in the last four months of the use year, any reservation to do so must be made before the last four months of the use year. For a Dec use year, such reservation would have to be made no later than July 31.
As to your rescission and commissions question, note that it likely really depends on what the contract for sale says. For example, that 10-day rescission rule may not apply. The timeshare statute in Florida sets out a long list of things a timeshare "seller" must include in a contract for sale, including that 10-day rescission period. Fl. Stats. sec 721.06. However, if you read the definitions applicable to the statute, the term "seller" excludes any timeshare owner who is selling his timeshare interest that he had purchased mainly for his own use, Fl. Stats, sec. 721.05(3). In other words, most DVC owners who are doing a resale are not subject to the statutory terms required to be in a contract for sale of a timeshare, including that 10-day rescission period, and thus you need to see the actual contract to determine the issue you mention.