How to help someone with PTSD?

My boyfriend dumped me last night after being together for 8 months because he says he has things he needs to work on, on his own. I know he has PTSD and some other demons. When we first started dating I looked up various things I can do to help him. I didn’t tell him about all of the different articles and forums that I read. I didn’t pressure him to talk about anything. I simple wanted to be prepared if he wanted to talk about it. He has shared some with me over the months that we have been together. I have tried my best to be understanding and supportive. I know that there are things that I will never understand or be able to help him with. How can I be there for him while not being able to be there? I really love him. How do I process this? Does anyone have any experience with loving someone with demons that you can’t help them fight?