I'm am a sufferer, and I agree completely with what you have said. I have a lot of anger associated with my PTSD and unfortunately my spouse is my outlet to vent my frustrations. There are times when I can control it, there are times when I explode and unload everything on to him, which he does not deserve. I know I do it, he knows why do it, sometimes I just can't help myself and he gets frustrated and fed up with me. You are human, it has to take a toll on the person standing on the outside looking in, wondering why theres very little anyone, even the sufferer themselves, can do to help. I can't imagine what thats like.
Just this week after over a year of telling myself I didn't need therapy I finally cracked and said I would go, for him. Sometimes it takes us hitting rock bottom to look up and see that there are better ways to cope, and that living life is still possible. For me, it took the realization that if I didn't do this I would lose him, the only real connection to "normal" life I still have left. He keeps me grounded. I want to say keep being persistent, but not at the expense of you. Take care of yourself at the same time.
Hang in there. I can't speak for everyone else, but I know that I am a challenge to live with, be with, and love. In the end I guess you have to reflect on why you are doing it, and hopefully that makes it worth it for you <3
I hope you find the support and advice you need here, this forum is a very good resource to get your thoughts out.
-SMC