InkScape can do proper 2D shrinking I believe. I know that with the stuff I do if they are closed shapes, I can set up for an offset distance from the path, either inside or outside.

Have you tried a vibrating tumbler? Seems a quick way to rid of the loose burnt remains.

Somehow though I'd miss the comments you make when the buffer decides to take one of your pieces and give it a toss. Be great to see a montage of all the events. Not to belittle the dangers and ruining of your fine work of course! 

Full HD video with surround sound please! 🤠