Why does this analysis show very high stress in a propeller?
The plots of your propellers seem to use a regular airfoil all the way to the root. Real propellers become almost cylindrical there, however. Also, aluminium propellers are hollow, so the outer part is only a thin shell, saving mass and reducing centrifugal loads significantly.

After all, real aluminium propellers work, so there must be a way to keep the stress in operation below the yield stress. FAR 23.907(c) even demands that a non-wooden propeller must be life-safe:


  The applicant must perform an evaluation of the propeller to show that
  failure due to fatigue will be avoided throughout the operational life
  of the propeller using the fatigue and structural data obtained in
  accordance with part 35 of this chapter and the vibration data
  obtained from compliance with paragraph (a) of this section.


Below is a drawing of a wooden propeller, but the outer shape of a metal propeller is not much different.



Drawing of a wooden propeller for the Fokker D VII (picture source)