You should definitely have a look at space engineers. They have a similar spherical problem with their voxels and I don’t think they went half as far as you did when implementing “orbital bodies”.
As someone who is rather keen on space, gfx, and the algorithms that render them. Kudos. The problems were known to me, which is why I didn’t attempt it, however - the distortion correction, the chunking, I’m thinking if you just limit how far down you can dig (half way to the “core”) it will be fine. You won’t run into those tiny squished blocks that make up the core.
It’s also important to call out the quad-sphere. This is what makes it doable. Naive devs may just map lat long to sin cos spherical coordinates and call it a day, not realizing that their poles are jacked up. The cartography problem. I’m really glad to see that called out as people don’t realize WGS84 sucks for mapping a sphere.