you are using a top down view... so you have to alter the Z index... which you have to adjust manually by events there is no behavior that accepts top down view jumps... as far as i know.
here is a example ZJump you can take the code and implement it in your game. and should work... now for the "fall trough gaps" you do the same thing... but it will be a bit difficult as you will have to either have another object that counts as "the empty fall area" or calculate offset overlap to trigger the "fall"
keep an eye on that example file in that drive, il work on it later il try add the "fall" also.