Thanks for the feedback. You seem to be playing an older version before we added auto detection on graphics and as such the system requirements are quite high. This version I considered to be too hard, as such the final boss's damage has been reduced. It's an early version so after you defeat that boss the game is over, you pretty much saw all of it by now. The main purpose of this early version is to gather feedback and find out if the gameplay is engaging enough to make more levels.
The jumping part is difficult due to your low control. A future update will give you more control over your jumps.
Checkpoints might be coming. The issue with checkpoints is that they cheapen deaths and remove from the tension if you know you can just retry an infinite amount so there needs to be a balance.