Thank you so much for playing! I'm glad you enjoyed it <3
About mitigating damage further, there are three skills available in the demo for that purpose:
Counter - Prevents an incoming attack and deals a small amount of damage to the opponent.
Sidestep - Dodge a projectile attack.
Burst - Prevents melee damage.
You may not have gotten any skills during your run (from either treasure chests or vending machines) or at least not any of the defensive ones -- sorry about that :(