Thank you very much for playing and the kind words! You can jump over the spikes in the last boss room without taking damage either by double jumping (easy) or by scaling the wall on the left and jumping when you climb high (challenge (but doable), because the shape of the wall requires somewhat well timed double jumps). :)
I get that some parts might be a bit hard/unfair, I guess I did it in an attempt both to make the game not too easy (it seemed easy from my POV, probably because I made it and playtested it ad nauseam (through all of the stages of development)) and to richly fill it with enemies, to make it more lively.