He was hanging around the wrong crowd and did something he had no clue on what bad things would really happen. Hes being tortured in his sleep and its very dark. He is getting weak and says they are after his soul. Im not familiar with anything you have to offer but, am willing to go to extreme measures to help my son.
I sent you a mail with some questions to see what advice I can give. I wasn't sure if you might consider a couple of them sensitive/touchy so I thought a private talk would be best. Though if you can be comfortable putting the answers in here as well it would help clarify the problem for others so they can help as well.
This is mainly my personal opinion but I do not believe any being can take a human soul. I believe you could perhaps give it up, but no being can simply take it from you. The details you have given are too limited to be of much help in determining your exact situation for certain yet based on the details one can make some educated guesses. I would assume this bad crowd your son became involved in was into the occult in some way be it big or small. Your son likely got involved either not knowing this, not taking it seriously, or it was darker than he expected. Either way now he believes, either because of something they said to him or some activity that he took part in, that he is cursed. It is more likely that his guilt, fear, anxiety, and stress have taken the shape of nightmares rather than him being cursed. There are methods such as banishing, cleansing, and protection related magick you could turn to yet if this is not some outside force but a emotional one these methods will not help. He mainly needs reassuring that he is safe, loved, and that his will is stronger than some dark force be it from the outside or inside his heart. Worry and anxiety as well as lack of sleep could easily contribute to his current weak condition. It is not impossble that an outside force is involved, but overall this is something anyone who's gone through a shock or tragic experience can feel as worry & stress can play havoc on the human body as well as mind.