PB Blaster is ok, but if you can get your hands on some Kroil, that's even better.I'd spray the entire assembly, especially the threads with PBlaster. & let it soak in.
After a day I'd start rapping the end against the door with a brass hammer to try to shock it loose,
Looks like the internet is full of arguments about both stuff LOL. As a last resort i'll purchase some kroil. Either way it sounds like it needs to be soaked and set for a while...is that correct?