Custom Transparent shader is not transparent

I am writing a, hopefully, simple shader which will allow me to do 2 things. The first is to layer several textures together using each texture's own alpha as a mask. This part works. The second thing is to allow me to use an entirely separate texture for the geometry's transparency. I have copy/pasted example code into my shader and it does not seem to respond to changes in alpha at all. When I change my base texture to something with an alpha, that alpha is outlined by an orange line in the unity editor. However I am not passing that texture's alpha to the SurfaceOutputStandard object. Regardless, the geometry is never transparent, and changing the blending has no affect except when it's "One One". All I need to wrap up this problem is to be able to use a 4th and separate texture's alpha for the geometry's transparency.

 Shader "Custom/multimage"
 {
     Properties
     {
         _Color ("Base Color", Color) = (1,1,1,1)
         _MainTex ("Base", 2D) = "white" {}
         _2ndColor ("2nd Color", Color) = (1,1,1,1)
         _Detail ("Detail", 2D) = "white"{}
         _Detail2("Detail2", 2D) = "white"{}
         _AlphaTex("Alpha Map", 2D) = "white"{}
         _Glossiness ("Smoothness", Range(0,1)) = 0.5
         _Metallic ("Metallic", Range(0,1)) = 0.0
     }
     SubShader
     {
             Tags{ "Queue" = "Transparent" "RenderType" = "Transparent" "IgnoreProjector" = "True" }
             ZWrite Off
             
             Blend SrcAlpha OneMinusSrcAlpha
 
         CGPROGRAM
             // Physically based Standard lighting model, and enable shadows on all light types
             #pragma surface surf Standard fullforwardshadows fragment frag
             //#pragma fragment frag
 
             // Use shader model 3.0 target, to get nicer looking lighting
             #pragma target 3.0
 
             sampler2D _MainTex;
             sampler2D _Detail;
             sampler2D _Detail2;
             sampler2D _AlphaTex;
 
             struct Input
             {
                 float2 uv_MainTex;
                 float2 uv_Detail;
                 float2 uv_Detail2;
                 float2 uv_alpha;
             };
 
             half _Glossiness;
             half _Metallic;
             fixed4 _Color;
             fixed4 _2ndColor;
             fixed4 _AlphaMap;
 
             void surf(Input IN, inout SurfaceOutputStandard o)
             {
                 // Albedo comes from a texture tinted by color
                 fixed4 c0 = tex2D(_MainTex, IN.uv_MainTex) * _Color;
                 fixed4 c1 = tex2D(_Detail, IN.uv_Detail) * _2ndColor;
                 fixed4 c2 = tex2D(_Detail2, IN.uv_Detail2) * _2ndColor;
                 fixed4 a = tex2D(_AlphaTex, IN.uv_alpha);
 
                 //Each texture is blended with the base layer in turn
                 c0.rgb = c1.a * c1.rgb + (1 - c1.a) * c0.rgb;
                 c0.rgb = c2.a * c2.rgb + (1 - c2.a) * c0.rgb;
 
                 //final rgb output is all the layers blended with their respective transparencies
                 o.Albedo = c0.rgb;
                 // Metallic and smoothness come from slider variables
                 o.Metallic = _Metallic;
                 o.Smoothness = _Glossiness;
                 //The final alpha OUGHT to be the AlphaMap's alpha
                 o.Alpha = a.a;
             }
         ENDCG
     }
     FallBack "Diffuse"
 }