Firstly it appears youve got the drive dogs from the rotor arm out so a pair of pliers or grips on the remains might get it turning so you can turn and pull to hopefully remove it.
Secondly, that flash shield looks upside down to me or at least not fitted in its correct orientation. Could be camera angles but the holes don't seem to line up correctly.
Think it's a matter of perseverance with the rotor arm.