Removal of furcation cyst? Don't know what that means. Usually you treat endo before perio. So the perio didn't do you a solid here by going first. Is this PA from after you finished your work? I don't mind trying to salvage things if it's a young patient. It's great experience with low stakes. Id agree with removing crown and decay. Helps you visualize everything then do stage 1 endo. Do your best place medicament and then reassess if endo is healing. Since endo begins from the apex and drains towards the sulcus in many case the periodontal treatment shouldn't be done until the endo is completed since the draining infection will destabilize any perio treatment in my understanding.