I do tend to think things happen for a reason to some extent, but I think sometimes it's hard to say what that reason is until a future time when we reflect back and realize the chain of events that brought us to where we are.
I'm also not sure that I could say that EVERYTHING happens for a reason. Things like CSA are senseless and horrible and I don't think anyone should have to go through that. The only reason that these things happen is that people have free will which permits them to do cruel acts.
In some ways your story reminds me of my own although I have never actually met my survivor. I also have faith in God as does my survivor. Over the two years that I have known him there has been a lot of push and pull. Sometimes he seems very open and close and he seems to really care about me. Other times he is very distant and pushes me away. He has told me that he goes through cycles and I have witnessed this. I'm not always sure what triggers these cycles since we are not together in person and I can't really see what is happening in his life during the times that he shuts down and stops talking to me.
I know he never means to hurt me though. He does lean on me a lot during certain times, but if I were to tell him that I felt used it would hurt him immensely. He was used by his abuser and he doesn't want to do that to another person.
You have to take care of yourself too though and if the relationship is bringing you down it is probably best to walk away and let him figure some things out. I am sorry for what you are going through.