Hm, let's see... Your health constantly drains slowly, so when I start shooting with no bullets, I hardly notice that I'm losing life. I played through half the game not realizing there was an ammo counter. Could be fixed with some visual feedback, like the player getting a hurt animation when shooting, or turning the bullets a different color... Something to warn them.
For the increased crosshair damage, again, there's no proper feedback when it happens. I did see that sometimes I dealt 15 damage instead of 10, but there was no indication of why that was the case. Maybe making the crosshair change when hovering over a target, or shooting a bigger bullet when in that state?
All these are just small suggestions, but the main gist is basically giving some form of feedback to the player to make sure they understand something is happening. Maybe you can think of a better way that fits your game!