Why have you ruled out the possibility of a sphere of stuff around the vast nothingness?
Do we have reason to believe that nothingness is primary while stuff is secondary? Isn't it possible that a tiny bit of nothingness, that is space, is all the nothingness there is and all else is solid stuff with no bounds? Just reverse your conjecture about what is . It would make no sense to ask what is on the outside of the stuff because like your cosmic design, there is no end to the stuff. I can just as well envision eternal but finite stuff with a hole of nothingness in whic some stray stuff moves around. All the stuff could still be in motion or at rest depending location of the stuff.