Hi A-man, I'm using a standard Blender build, standard physics settings and standard Blender game engine to run the simulations.
I am using my own tools to, amongst other things, create the voronoi shards, calculate the mass and center of mass of each shard based on their volume and material density. My tools for Blender are not finished, still a work in progress, but I did release the source code to create voronoi shards (and calculate their mass and center of mass) for Bullet Physics. That source code is now included with Bullet Physics Library since v2.80.
Physics settings: beyond having correct relative mass and centers of mass, the only setting, and maybe single most important setting is that all rigid bodies are using collision bounds, without exceptions. Also I never use Triangle Mesh bounds, only primitives or convex hulls, so I break down non-convex objects into compounded convex hulls (convex decomposition).
Floor: Unfortunately Blender doesn’t implement Bullet's "Plane" primitive collision bounds, so your floor should use "Box" collision bounds, it must have a good thickness to be solid, and it must have a margin, typically 0.04; otherwise objects will fall through it and/or not have stable collisions.
Scale: Bullet Physics is comfortable with meters. Standard Blender scale is treated as meters, which is ideal, but you don’t want to use objects that are too small. If you want to use a smaller scale, you should increase gravity and FPS instead.
It helps to understand Bullet Physics to best use Blender's rigid body physics. This would probably require an in depth tutorial, and there may already be some out there, but all I can really suggest is to read the Bullet Physics Library manual. Problem is that it's a little too technical and targets programmers, not end users.