Child services isn't gonna do a thing if there's no evidence of physical abuse, especially not at the age of 14. LW can call them right now, for all the good it'll do.

What LW ought to do is speak to this boy and ask if he has any other relative or friend he'd rather stay with. Then, depending on what he says, LW should either speak to his mother about either a. agitating for full or at least half custody or b. agitating for him to stay with one of those other relatives OR LW should offer to "help Friend" by "taking her difficult stepson off her hands". Which you'd think is a fairly transparent ploy, but you'd be amazed at how many people would, in fact, sign over permission for the kid to stay at somebody else's house most or all of the week, every week. You could even do it very informally if he's already enrolled in school and an actual parent can reliably be called should he need medical care. Which might be the only way to convince the wicked stepmother and her equally wicked husband to do this. (I don't really like doing an end run around Mom like this, but the most important thing is to get the kid out of that situation.)

Of course, maybe nothing can be done short of dropping scholarship applications for boarding schools on Kid's desk.