Perhaps the camera drifting is due to you having a controller plugged in? Anyway, I plan on adding controller support so a simple deadzone will fix that issue eventually. The dummies have a certain HP before they explode, in the screenshot you posted, you were using a birdshot cartridge, it has more pellets, more spread and lower damage, these are more suited for taking out drones (coming at a later update).
Thanks for the feedback!