I've tried reaching out to him about it, I've also tried to ignore what he told me and go on as if nothing was said. Nothing has worked. It seems like no matter what I say to him, it just ends in him getting mad about what he told me.
You can't ignore/forget what he said to you and he knows it. The disclosure has effected your relationship and nothing can change that. Of course he is mad about telling you because this has changed everything
as far as he is concerned.
I can't live like this forever, however I also do care for him and want to stay with him and help if I can. I do not want to abandon him, especially because this behavior is most likely because he was a victim... but I don't know how much more I can take. Even though he claims what happened "does not affect him and it doesn't need to be discussed", it is clear that it does, and as a result it affects both him and me.
You can't fix him. He needs some professional help. But he has to also want to deal with it. And it wont be easy. It never is. While it would be good (if he decides to deal with it) for him to have support I don't think that this could be the only reason for staying with him.
Whatever you do will be wrong. It always is. But you are already getting that.
Remember that this is just an opinion based on my view and little information.