What a night! I had a a few ideas - but actually, somehow nothing worked out. Almost all experiments failed, the volumes acted strangely, the noise was screaming / denoising didn’t help and preview and render window didn’t match. I think the whole “in the zone”-thing just didn’t work tonight. In the end, I changed my plan, started over and went with a fast and simple one. Maybe some sleep will help. Good night. 
“Scatterbrained Thimblerigger”
non competing (pure), cycles (512 samples + denoising)