Well, I own level 9(purely) but Pikachu actually IS more difficult then the others.
Projectile: Either do a sidestep or mach tornado to either evade or neutralize the projectile.
Thunder(DownB): theres alot of option here. First, a good way is to start a mach tornado before entering the stage again. This will neutralize the attack and you will not be damaged. Another thing is that you aeriel dodge it. Or, the technique I use, do a downB(teleport) and direct it to the stage when your on the same horizontal level as pikachu and make it land behind him, this causes Pikachu to fly off the stage. If you miss, Pikachu will still have some lag and that opens a small attack to you.