Skybox Mesh Mask Problem

Hello,

I am trying to implement a day night cycle visual effect to my game in Unity and I wrote a shader for it.

Right now it looks like this:

The problem is that I want to be able to change the skybox (blue background layer) individually but the shader I was able to come up with effects everything behind it.

Here is the shader code: https://paste.ee/p/9tyEX

Also this is a mobile game project so the solution must be very performance friendly.

I am open to new aproaches as well as improving this one. I wasn't able to come up with any thing that would let me change the backmost layer individually. I am new to shader coding so I thought I might find some help here.

Bonus GIF: https://gfycat.com/gifs/detail/CarefreeLegalElephantbeetle

Thanks in advance!!!