I drink potion of night vision, and it's still dark as if no effect applied.

Your screenshot has night vision applied, so it's working.

Do you mean the blueish effect? That's quite darker than vanilla one.

And the part of the locomotive (Railcraft) in the steam is wrongly culled

Origin mod has some origins that have night vision, which won't work with this shader either.

Your screenshot has night vision applied, so it's working.

Regarding the object's culling, it seems more like an issue with the mod or the underlying technology (Iris, Sodium) rather than the shader itself. There's nothing in the shader that can fix incorrect culling. Sorry about that.

I must add that the technology used in Minecraft 1.12.x is so different from the current one (which has already changed twice since then) that the support provided by the shader is legacy. There are no plans to extend support for mods or features related to anything prior to 1.17. Sorry about that.