Cant seem to render alpha surface shader BEHIND geometry

Hello there. I'm attempting to add a spherical 'glow' behind my planets in a space exploration game. There are 2 issues:

1) I can't seem to get the effect to render before (behind) the geometry in my scene. I've tried setting the Tag as "Queue"="Background", "Queue"="Geometry - 1" in combination with both "RenderType"="Opaque" and "RenderType"="Transparent", all without luck. The planet surface is rendering in the Geometry queue and I've also tried adding a 'forward' offset to that. Both the planet surface and the atmosphere glow seem to be jostling for render position, creating a frantic, moving mosaic. That looks real bad.

2) When I include this line...

 #pragma surface surf Lambert alpha:fade

..I get the alpha effect, but then the entire object disappears at distance. This being a space game, the distances are large, but I'm talking about a few thousand units. When I don't include the 'alpha:fade' part, the alpha does not render (everything is opaque).

Here's the surface shader, which gets passed an atmosphere tint Color and an atmosphere density float.

 Shader "Custom/planet glow" {
     Properties {
         _glowTint ("Glow Tint", Color) = (0.5,0.8,1,1)
         _atmosphereMix ("Atmosphere Mix", float) = 0
     }
     SubShader {
         Tags { "RenderType"="Opaque" "Queue"="Background" }
         Cull Front // I want only the far faces to render (behind the actual planet surface)
         
         CGPROGRAM
         #pragma surface surf Lambert alpha:fade
         #pragma target 4.0
    
         struct Input {
             float3 viewDir;
         };
 
         fixed4 _glowTint;
         float _atmosphereMix;        
 
         void surf (Input IN, inout SurfaceOutput o) {
             o.Albedo = _glowTint * _atmosphereMix;
             float cameraNormalDP = saturate(dot( normalize(IN.viewDir), -o.Normal ) * 4.5);
             o.Alpha = cameraNormalDP * cameraNormalDP * cameraNormalDP; // makes the edge fade 'faster'
             o.Emission = _glowTint * _atmosphereMix;
         }
 
         ENDCG
     } 
     FallBack "Diffuse"
 }

If anyone has any pointers as to what I'm missing, that would be great! Cheers.