When does your son go to the army? I think it would be very good for him, to get away from this bad bunch of kids he hangs out with. And hopefully give him self esteem.
Is there any organization in Israel that helps kids who are off the derech and their siblings? In america, Project Yes used to have a mentoring program for siblings. They would go out once a week to do something fun and talk.
Aries 2756, I very much like what you have to say. Unfortunately it is probably hard for write or wrong to follow your good advice, as her son is trying very hard to make everyone miserable.