Exact same answer as before. I am not sure where the hangup is.
You are mis-using the LayerBlend node. As I said many times, do not use it anywhere in this material. It does not work with functions.
All you have to do is hook it up like my image where I hooked up a LayerSample to your alpha.
And you can use HeightLerp. You simply use the “Alpha” output pin without ever using A or B inputs. Please load up the content examples map “Math_hall.umap” and see an example of exactly that.
>>Just imagine that all the (Non-Alpha) Texture samples are Material Functions.
That is exactly what I am trying to help you set up. That is the entire reason why material functions and “matlayerblend_standard” functions exist. We made them for exactly this purpose. I’d like to help you but I cannot help you if you do not try what I suggest.