My 2 cents: You need to convince him to turn himself in. I also think it should be done in conjunction with being in therapy. Best case would be for him to discuss this with a therapist to gin up the courage to confess to Clemson and to gain some insight on why he did this. Can you afford to pay for a private therapist for him?
If YOU turn him in, I do not think he will learn from it. He’ll be resentful and angry going forward. Given that he comes from a tough background with unsupportive parents, I predict it would be very difficult for him to recover. OTOH, if he turns himself in he creates an opportunity to feel better about himself, more whole. It could help his self-esteem if he engages in an act of integrity.
As for you . . . have you breached your employer’s security protocols by allowing someone else to use your work laptop? If it was your personal laptop, why was your employer’s letterhead on it? That is a breach of security as well. This might be something to consider as you move forward.