Enemy health was way too high given the twitchy nature of the action. I started resorting to grouping them up, standing in place, and detonating the bomb so it would guaranteed kill multiples of them at once.
I know how hard it can be to vary enemy movements without having them collide up on each other. My game has the same issue. If I'm going to have a lot of enemies clustered together and running in the same path, I often assign them movement speed values in a random range so they stagger out a bit. You might have done that but I couldn't tell. Lol I was focused on shooting.
Cool concept though. The few times I got a kill combo and my gun started spraying bullets it was both satisfying and conceptually terrifying as I knew I was dumping health. Good job!