Those are all valid criticisms. Short reasons for all of them:
Pixel inconsistency: No artist on the team ;p
UI too big: Was brought up by our testers but there were more important things to fix first.
Game too easy: For a jam I prefer a game that most people can finish. Maybe we could have made the boss more difficult but with a not so great build he is very hard to beat.
Loved your review because it's good to know where we can improve and of course we are happy you enjoyed it! :)