hi. i can help your problem
the reason why your actor fly when you press jump because you dont input the gravity at the scene.
1. select and open your scene
2. choose physics at tab scene.
3. input the gravity. standar gravity is 85.
but you can input what you like. im sugest to use 120 gravity.
btw i need your oppinion about my game.
there is my link
http://www.stencyl.com/game/play/20164thanks