Good point about the probabilities, you're totally right. The safety rolls complicated things (by making it more likely), and I decided to take out safety rolls completely in the post-jam version because they're unintuitive when you hear the premise of 6 - 5 - 4 - 3 - 2 - 1. And you're also right about the rolls! They're totally not fair, with each missed roll weighing the dice slightly in your favor, but that's a secret mechanic to make it more fun (and less fair)
I really appreciate the thoughtful feedback! Thanks for your comment :)