It kind of concerns me that D21 is already making excuses for OMs behavior. Not saying that we shouldn't have compassion for the mental health and addiction issues of others, but seriously.... Your kids should not have to be exposed to this chaos.
D19 may be much happier living with your sister, out of the chaos and able to get to work by herself. Does she have a bike? If not, can you get her one?
As for S14...... What does he want? He's old enough that the courts will take his wishes into consideration.