The jerking is due to the scrollingY and the 8direction movement going up actions. You don't have to move the Smurf upwards. You want the fruits and rocks to fall down.
I changed those things and I am attaching the capx (I removed the music and some images in order to reduce the file-size and be able to attach the file).
Overall the game has a nice aesthetic, the music is kinda on the loud side and the fact that it's only 8 bars doesn't' help.