Thank you for the feedback. We are glad you enjoyed our game :)
To address your points:Regarding the checkpoints, we probably should have named it differently to avoid confusion. They are there only to check whether you are a proper Doomslayer and do NOT serve as a respawn point. We felt like it would be too easy with actual checkpoints.
The limit of 50 bombs is there to force you to think carefully about the placement. With that said, 50 should be plenty enough even if you don't play the optimal run. We keep the best score so you can always try to beat the level again using fewer bombs. However, I understand the Doomslayer's urge to just run wild placing bombs everywhere :)