I would suggest taking the Monorail to MK, then boarding a bus to BW.
Alternately, if Epcot is still open, you could walk to the TTC (or take the Monorail to TTC). Get on the Epcot Monorail, enter Epcot and walk to the International Gateway to BW. This would require a Park Hopper ticket.
Not sure about the direct buses, but the monorail options may no longer be available. I did read that monorails were closing 1 hour after park closing and I'm not sure if they will be operating during the parties.
Not sure about the direct buses, but the monorail options may no longer be available. I did read that monorails were closing 1 hour after park closing and I'm not sure if they will be operating during the parties.
True, I share you concerns. One question comes to mind. If Epcot is open to 9 pm (as normal), meaning the Epcot monorail is open til 10 pm, wouldn't it be reasonable to assume that at least the resort monorail would be open until 10:30-11 pm, to catch traffic off of the Epcot monorail at the TTC? Even if MK had been closed for more than one hour?
Since you're going on a Halloween party night, there will be buses from the Magic Kingdom. If the monorail is still running, take it to the Magic Kingdom and pick up the bus back to the Boardwalk. If the monorail isn't running, you should be able to catch a boat to the Magic Kingdom, instead. Either of those options are better than the Epcot scenario.
If the Resort Monorail is still going to be operating because we don't know how things will be on nights when the Magic Kingdom is having Mickey's Not So Scary Halloween Party, you can take it back to the Magic Kingdom and get on the bus back to the Boardwalk. Worst case scenario if the Resort Monorail is not operating you can take the boat directly to the Magic Kingdom.
Although another option is taking a Taxi from the Polynesian to the Boardwalk, assuming you don't mind the cost and it will be a lot faster then any form of Disney Transportation.