I looked in to a system called flash fog. Although it is really cool and will screw you up when it goes off it is just way out of my budget right now. It is a pretty affective system though.
I love this system and I am sorry that you are having all the problems even with what seems like safety glass they still aren't dissuaded. Maybe you could deter them with some smoke bombs on a trip wire. I don't think that would technically qualify you for any trouble but it may dissuade them. Or for that matter they make trip wires that take 12 gauge blanks, I am not in the habit of stealing things but a 12 gauge in a 4 inch barrel would be loud enough to make me skidaddle and probably buy new underwear.