A updated your capx with a range display. Here it is Fixed Example - Range
You should make a sprite with a circle shape. Then put it on the game, outside the layout, on touch set position to touched object, send it to the back, and you could set the size to the tower range (so if you have different towers, it will show an accurate range). What I also did;
I split the layout in two layers: BG and Game.
This is mainly a way to easily place things using Z order without complicating it too much. I created an empty 'BG' sprite, and the circle sprite called 'range'.
Here are the events that place the range:
<img src="http://i.imgur.com/R0oHstF.jpg" border="0">
And here the ones that puts everything back:
<img src="http://i.imgur.com/hgtJ3XQ.jpg" border="0">