Maybe I'm not qualified to answer, as I HAVE PTSD, but I also decided, at one time, to file for divorce.
My ex has since died, so my therapist has never met him. He says, from my descriptions, it sounds like he was a psychopath, a narcissist, or both. When we got married, I had kind of an "I really don't care" attitude that was probably at least partly a PTSD related reaction to other life events. I tend to deal with things by going along to get along, until I get pushed past an invisible line, then I blow up.
We were married for 12 years. Towards the end of that time, I realized that our relationship was pretty one sided and that began to bother me. We had a history of infrequent but loud arguments that never really got resolved. (They'd usually end when I got so mad I wanted to kill him and I realized that wasn't a good option AND we weren't getting anything accomplished. At that point I'd walk away. He'd let me, and then go on to act, later, like nothing had happened. That always freaked me out, because that kind of argument looked like Armageddon to me.) The arguments got more frequent and I got less willing to back down. A day came when he started something that I thought was totally unreasonable. I clearly remember looking at him and thinking, "I'm not going down this road one more time." Even though saying "yes" to his original marriage proposal was impulsive and poorly thought out, I took the whole "marriage" thing pretty seriously. I never threatened divorce. (Actually, I never THREATEN anything.) We tried marriage counseling. The first session, the therapist said there were 3 options: live with it like it is, change it, or get out. I said I wasn't up for option 1. A couple weeks later, my ex announced that he was too old to change. I resisted the impulse to walk out right then, stayed till the end of the session, went out and found a lawyer, and filed for divorce.
I'm not sure your partner having PTSD is really a factor in the decision. The relationship is either working or it's not. If it's not, you both either have the will and the potential to make it work, or you don't. One partner can't, unilaterally, decide to make it work. Not really. One partner can only, unilaterally, decide to deal with the status quo, or make changes on their own side. It takes active involvement by both partners to make a truly good relationship, IMO.
I think you have to ask yourself what's causing you to feel worn out, and honestly answer the question, then decide what can be done about it. And you should run this by your partner. Could it be that you're taking on responsibility for stuff that's actually your partner's responsibility, not your own? That could be pretty exhausting all by itself.
