Best way to add a gradient masked layer but mask out subject
I am looking for the best non-destructive way to achieve the following. Any recommendations on how to setup my layers to meet the following?
My first idea is to create a new layer by merging everything that is visible (ctrl + alt + shift + E), then applying a layer mask and removing the subject's legs. It's not my preferred method since I don't have the ability to easily adjust the gradient later on.
I have a black color layer with a layer mask. The layer mask is a gradient black/white applied to it.
Why: I want to create a fade from the bottom (black) to the bottom 1/3 of the image (white), to keep the original floor of the image but fade into a blacked out background.

I want to mask out the subject's legs so the fade is not applied to the subject and appears to occur in the background/on the floor behind the subject.

Very rough example of the desired before & after:
Before (black background layer disabled)

After (black background layer enabled with subject's legs masked out) --


But, I want a way to mask out the subject without it affecting the original gradient that was applied. This way, if I make a mistake and mask out part of the background, I can use a white brush on the background so the original gradient is still applied.
If I use my original layer mask and mask out the background, I cannot apply the original gradient to the background.
