Hey sorry this is a bit late, but I wanted to still thank you for your lengthy feedback post!
About level 5, during some playtesting the players did not even realize some keys did not float, so I thought it would be fine if more attentive players would just solve the level by looking. Having to repeat the level just by luck did seem a bit unfair x)
And the moving enemies were definitely a not fully worked-out addition. Yours is a good suggestion to improve them!