I don't know how much you have read here on MS. There is a lot to learn.
He could actually stay in this state, in a functional manner, for years. I'm not saying that he is going to, but it is a possibility. What he really needs is to learn about PTSD, triggers, dissociation, and all kinds of things. He needs help. He needs support. He needs to know that he is not the only person that this happens to.
To some extent, he will also learn that his entire life is basically a lie. In one way or another, he has been dissociatiing throughout it. With CSA, many things, including love and trust, are twisted and distorted and intertwined with feelings of anger, pain, guilt, shame, and all kinds of other things. Until he starts to learn this, and fight against it, and get rid of it, he will have an extremely difficult time ever trying to learn or understand how things actually are supposed to be.
Right now, absolutely nothing makes much of any sense to him. It's all meaningless. It's all hopeless. He reached for what he thought would be an opportunity to confront this and face it head on and be done with it and free from it forever, and it failed. Unfortunately, even if he had succeeded, it still would have failed. This will never go away overnight. It takes hard work, determination, love, understanding, support, and all kinds of things, inclulding time.
"Every child asks the questions which hold the answers to the secrets of the universe, WHAT?, and WHY?". --Me