1. You don't need to change sprits, you should change them by animation. And coding for that should be somthing like...
ALWAYS
IF X Speed of self = ( what ever your right movement speed is) ... Set aminamtion to ,move right,?
If X speed of self = ( what ever your left movement speed is).. Set animation to , move left,?
I think this will work? But I've never tested it? It sounds like it will work though?
2. For the death behavior for scrat, do....
If actortype (enemy actor type you want), collides with actor type( scrat )... kill self, reload scene.... Just do that with every actor type you want to kill scrat... Or you can do it where you can make a new actor group called enemy, and make it where if scrat collides with any actor type in the group , enemy , he dies and reloads?
3. Obviously, you messed up somewhere with the tiles? So I would probably just download a tile from Stencyl Forge.
4. One reason that scrat might be falling from tiles, is that not all the tiles have collisions shapes on them? Another reason could be, that scrats collision boxes are out of place and misshaped? Or the reson could be, some animations don't have any collision boxes?