The Domain Shaders function exactly like a Reference Shader. This gives you the luxury of changing a single shader and having it automatically update all objects in a scene that have used it in a domain instance.

So, if you create a material "glass" and change the color, all objects that have been told to use Glass in the Properties Palette domain area will be updated. 

So, in your case, the only need to prepare one pawn and and then duplicate it once the domains and shaders have been correctly assigned. Same for other items.

To delete a Layer List item, simply highlight it and press delete/backspace on your keyboard. 

Dealing with imported objects is throws a bunch of variables into the mix. Low res and free models have usually been prepared by less experienced 3D modelers that may not be familiar with all of the protocols for exporting "generic" formats like .obj or .3ds from their modeling packages so that they work well in other programs (this can even be true of pay-for models on occasion too). This can result in domains that don't play nice in Carrara. Sometimes, the best  way to get domains to work well is to trash the original domains and recreate them. 

**The issues you are encountering with your objects and shader domains is likely tied to bad UV coordinates when it was exported. (some programs modify UV's on export and don't let you know) There may be overlapping UVs that are effected by domain orders because the hierarchy of the domain list gives priority on a first come, first serve basis. If this is the case, there is nothing you can do but remap the UV coordinates for the object. To see if this is the case in your instance, select the object, go to the Vertex room, enter UV mode and from the Display tab in the Properties Palette, select "Show All" from the shading domain list. If you see overlapping meshes in the UV window, that is a problem that you'll have to sort out manually.

Mark