Well, after checking your scene, the most basic problems lies on your scene scale, your object scale relative to scene is very big, for example the 2d player has a 12 units scale on every axis, and the ground is also so big.
I'd change the scale for the sake of tidiness (scale everything back to one, and then scale the ground accordingly), but if its too much of a hassle, you can change the gravity value under physics setting (under project settings)...
here is the scene I've modified, just put it inside your asset folder, and then open it up, also change your gravity value, because that setting depends on the project, I've change it here, but yours may stay the same, so you'll have to do that also, I
ve set it to -250, and it is all good...
PS: I've created a new FSM for jumping, and disabled yours (but not deleted it)