tension

Hi all, I have a 2013 lx570 with a rear wiper issue. No tension to the rear windshield, kind of flops around if you will, motor is still good. Popped the rear cap off, moved the arm up and to my surprise it pulled right out. Is this normal?

Does anyone have any suggestions for tools to remove this tension nut? Have tried screwdriver and hammer clockwise and anti clockwise.