ds 15 saved his girlfriend's life last week. She had locked herself in her house and taken 30 strong pills. He managed to climb in a first floor window and call an ambulance which undoubtably saved her.
He now believes that he needs to be available to her 24/7 by text or nearby presence in case she trys again.
The relationship was complicated to start with as she is a troubled girl. He's walked out of class and hitched to see her when she's phoned him up saying she's going to kill herself. He's gone to see her in the middle of the night etc.
Last night he admitted that this was why he's refusing to come on holiday with the family. He said he felt like it was his mission in life to be there for her and that if she did succeed he would probably kill himself too. 
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I've tried to keep it calm and explain to him that he needs to find support for himself in order to support her , but he's not open to this and thinks he, and only he can do it. He doesn't trust the other people she has around her to watch over her well enough.
The relationship was already pretty abusive IMO with her blowing hot/cold and being very controlling , I understand that she clearly feels out of control and this is why.
How can I protect my son from what appears to be a codependent and damaging first relationship ? He's clearly worried sick about her, he's not eating , he's erratic and very angry with us all inspite of having a lot of understanding and support.
He's had a very traumatic experience, but he clearly can't be her caretaker and I'm worried that him playing this role is putting her potentially in more danger as there's clearly an unhealthy dynamic going on.
How can I help him. At the moment in between shouting and swearing and threatening to run away he is actually opening up occasionally and I don't want to close this off by being heavy handed.