I cannot find the amount that evolution is reduced by per research. What is it?

0.004

I can change it to custom or dynamic values like 1% if needed.

A flat subtractive 0.004? That aligns with what I seen.
I am a bit puzzled as to when this would be effective. It's very cheap to make and requires only red science so it can be ran in-between other researches but since its a very small subtraction you'd have to research it many many times to see any significant effect. Meanwhile your pollution could offset it.

When you designed this feature, what was your vision of when it would be beneficial?

This is a product from when I was learning to make mods. At that time, I didn't consider overly complex variations; I just researched it to completion, which reduced the evolution value by 0.004.

Inspired by InfiTech