Particle collision and display

hello everybody,

this is my first post, so i'm a noob  :lol:

I'm working on a game where the character can use magic power to throw water and i would like to allow him blowing out flames. So I tried to setup a collision between the water and the flame.

The problem is that the bounding box of the flame and the water doesn't fit their respective particle, it's too large. isn't this bounding box calculated automatically ? What is the better way to handle collision between the water and the flame without too much calculations.

An other problem is that I can't stop emitting water when the player stops pressing the button, because the stopEmitting() method seems to be effectless. What kind of mecanism should i use to enable/disable throwing water, because attach/detach child method seems to create some display problem : with this method, the particles are displayed as colored and not textured quads.

Last problem is that the flames seem not having the same color depending on what there is behind them : if the background behind the flames is black, the color of the flames is quite realistic, but when the background is not dark, the flames are too white, what parameters must i change ?