If MK is open when you want to get to the WL, you can just take the MK bus from the POR and then take the WL ferry from the MK.
When you leave the WL you can take a bus to one of the parks that is still open and then take your resort bus from that park, or if the MK is still open you can take the ferry back to the MK and your POR bus from the MK.
If it is really late when you leave you will need to take the bus to DTD from the WL and then get the POR bus back to the resort.