I'm confident the DVC owner will be paid in full per David's usual policy of paying part of the rental fee when the reservation is made and the rest on check-in day, whether it's the OP who checks in, a new renter or nobody at all. The OP has already paid David's in full, the DVC owner has already received 70% of the money that's due to him/her and will get the rest on check-in day.
Reservations through David's are normally non-refundable. In this particular situation, David's is offering to help the OP by making an exception to their "no refunds" policy by trying to re-rent the confirmed reservation provided the DVC owner is open to changing the names on the reservation and arranging anything else needed by the new renter (DME, dining plan, etc). If David's does find a new renter for this reservation, the OP gets their money back minus $4 per point that David's will retain for their efforts. I suspect part of this fee will be paid to the DVC owner for agreeing to re-do everything on their end. But in any case, whether the OP goes on the trip, or stays home and forfeits the full cost of the trip, or agrees to (and David's is successful at) re-renting the reservation, I'm quite sure the DVC owner will be paid in full.