In term of game design it worked well. In fact I hace only shitty rolls at the beginning (failed all my 4 first roll even using traits). My personnal die went quickly to D4 so I decide to accept a devil's bargain with the Saturn. This mechanic is very powerful because I had a total refresh and didn't had problems to finish the investigation then. The thing is, the more clues you find, the more quickly you solve the mystery (I made a final 15 with a 10 and 5 clues). So rolls are very important and could be a critic to your game. But my own game also is very hazardous and I think it really fit with the genre.
The only regret I have it's focused on only one objective. Your just the gumshoe looking for the truth. Perhaps it could be great to add some breaks between two investigation scene. Perhaps just narrative scenes or opportunity to refresh a dice.
That is a very cool setting.
And it confirms my suspicions on how the game would go. It feels very swingy right now: a few failures early on will cause a very quick death spiral, while a few successes can quickly solve a mystery. That is part of the reason for the devil's bargain mechanic, to give a player a way to escape the death spiral but at a cost. Over multiple mysteries, I hope it would work out to an interesting punctuated rhythm of play.