Hi, great game! I've got a few thoughts if you don't mind.
First I'll suggest a little bit of head tracking when the main character aims up or down. It's a little thing but I think it'll add a lot to the visual aesthetic.
Second, add me to the list of people who'd like some more permanent progression. Something so when a person hits their skill wall they can still progress towards improvement.Some examples might be taking X damage eventually gives you the ability to start with an Aspirin, X times 10 and you start with Morphine instead, X times 100 and you can also buy one free Morphine each experiment attempt, and so on.
You could also give points to upgrade the basic pistol the more someone does damage with it. It would get an ammo pool like other weapons and when out of ammo, it reverts to the basic unmodified version until more ammo is found or bought. Things like clip size, ROF, damage, accuracy, as well as adding special abilities could be modified.
Thanks for the game.