The heart slots are mostly to do with how you got the pieces. You got the crumb from the gluttonous guy, glass from the slothful guy, wood from the envious guy, and the jewellery is left to represent lust.
To beat challenge 6, don't worry too much about avoiding orbs in the beginning. If you lose to the time limit and you have lots of health left, you haven't spent your health wisely.
Ah, I see what's happening now. If you click and hold on the next or prev buttons and move your mouse around the button at the same time, it skips over multiple levels.
The handling is awkward, and the way that it changes as the player accelerates is just annoying. I suggest that you improve the handling and increase the number of obstacles. You could make this more fun without reducing the difficulty.
Relies too much on luck in the late game. If you guaranteed a powerup for the first area destroyed, and if you made the total playing field, say, 30% smaller, I think it would be more fair. I also think it's too long. 40 levels should be enough.