Did you read the part where I said, "Thiswebpagehas an excellent animation that you must watch. The worst case for stress may not be when the contact is at the pitch circle."?
A big difference in stress is expected when the rotation angle changes because the contact point moves in and out from the pitch circle. The bending equation depends on the actual location of the contact point which is moving with rotation angle.
There are no analytical equations for the stress in a helical gear, you have to rely on numerical simulations.
There are analytical equations for simpler geometry like a four point beam bending geometry. Ansys simulations have very close agreement with those equations.