Block on blocks?

Hey, sorry if this question has been asked already, but I'm trying to make a superhero game. I downloaded Hulk and Spider-Man sprites, and I want to make a long stair case. My idea was that the hulk would destroy the lower steps, while Spidey climbs the steps. The only problem is that the steps I made won't fall, they just hang in the air. Plus, they look messy. And they keep falling through my floor sprite.

So I'd like to know:

1) How do you make a neat pile of bricks?

2) How do you make the bricks fall?

3) How do I keep them from falling through the floor sprite?

Normally this would be done with a sprite animation of some bricks falling. You could use the physics behaviour on individual brick sprites to make them fall and bounce but this seems redundant. For them to interact with the floor you need to make it solid or you can try a physics behaviour with immovable set to Yes.