What I learned from your .3dm file is that you want a shape like this:
I did something similar recently:
Your GH file doesn’t help at all. One bit advice is to aggressively disable preview on upstream components so you can see what you’re doing.
I copied your goal geometry into the version ‘d’ file I posted yesterday, bypassed the Voronoi bits since that part is already done (manually?), and got this:
Voronoi_2021Oct11a.gh (508.2 KB)
Geometry is internalized, no need for .3dm file.