IMHO, the best option after dinner is a cab. For me, it would be well worth the $12 - $15 to avoid being part of the crowd leaving the MK at closing. And I'd be back in my room within 15 minutes or so.
If you want to take Disney transportation, my advice is to take the bus to DD and transfer to the POP bus there. Again, I'd rather sit on a bus or wait in an uncrowded area than be part of a crush of people all trying to leave the MK at the same time. If that doesn't bother you, then yes, take the monorail back to the MK and walk over to the bus area to catch the POP bus. I'm not sure it would be quicker than going via DD at that time, though - you may have to wait for more than one bus if there is a long line at the MK POP bus stop.
Best wishes -