First off if you are having trouble, save scum. It's frowned upon sure, but if you're okay with that after each level, save and quit, then copy your "interim save" to either a flash drive or the cloud, then resume the game where you stopped.
The best advise for the third level is to repeat the same movement pattern with Pac-man until you can get a consistent positive ghost position; if a problem arises, restart (or reload) and try it again with slightly different movement.
An important thing to remember about ghost movement after eating a power pellet is they will go in the opposite direction, but that is sometimes to your detriment, as they would have gone away from you one way, but instead head right towards you, normally quite handy but not here! I found eating a pellet when they were stacked less helpful as it was harder to tell where they would branch off to.
I found myself with only a few dots left, but cornered so many times. Good luck!