Thanks a ton for such sincere and solid feedback!
Your idea about unlocking calamities in round-based waves is super neat—it actually mirrors my original design almost completely!
I actually split Death's calamity deck into different tiers (high-tier calamities like Amnesia force players to discard their hands). I also added counterplay mechanics where both Death and the player use perks and items to basically "cheat" against each other.
Also, spot on with the playtesting workflow. Since Death is currently the sole enemy, I actually wrote a python script to simulate game loops and dial in the length. It spat out an average of 33–44 rounds per game, which hit my target duration pretty well—though that was before I cut the perk system due to the jam's time limit. But as you said, nothing beats that rapid "tweak a number in two seconds and playtest" loop in a jam setting!
Thanks again for the great dev-to-dev insights!