Issue with fog of war via PPV

I am working on an old fps style fog of war, similar to Alien Trilogy (psx) and others but I have run into a problem I am not sure how to fix.

In this first image on the right side there is a box in the distance.

After just a rotation of the camera, it becomes more visible, so the ppv material is essentially a box around the camera I am assuming.

Here is the blueprint that I just put into the blendables array in postprocess volume.

Is there a way to make it spherical, to avoid “longer sight” in the edges of the screen?

You can just use a SphereMask node as alpha input for your lerp.