The important thing here is that you DO NOT release the sparkys...
You can quickly make their chambers smaller by deleting a far left block, dropping into the space, and creating a new block down inside the sparky box. Do this enough, and you'll limit them to a much smaller area, leaving you the necessary two block column available to descend to the key and return to the door.
1) Climb one side and remove fireball shooting dragon.
2) Descend to the other side and repeat.
3) Move to center and drop down to retrieve key.
4) Climb back up to door.