I understand that with the bolt carrier back in the buffer tube the rear pin being puuled will not let the rifle hinge open.However,I just read about a similar problem on another thread.If you pull both the front and rear pins,the mag well end of the reciever should swing away.
On another thread,one of the true uses of WD-40 was discussed.It is pretty good for killing primers,however,think real careful about this.The powder in the case is only going to allow the bullet to deep seat so far and the bullet may not seat deep enough to allow the oil to kill the primer.The cork might still plug the bottle.My point is,try the oil to kill the primer,but assume the round is still hot.Your cleaning rod may become a projectile,and without a bolt in place,the barrel will shoot out of both ends.
With the rear of the upper receiver resting on something hard,like an aluminum plate on concrete.you may be able to just let a cleaning rod drop 8 or 10 inches (Keeping your body well clear of the danger zone) a few times
Don't bother with a broken case extractor.They are for when the case head is ripped off,and just the forward part of the case is in the chamber.
And,yes,you do ave to be concerned about the crown every time you put a rod in from the muzzle
Good luck.