It is great that you are being honest with yourself and how you feel about the situation.
I also understand being in a stable relationship due to a need for stability.
But what I am learning is that even though the one we picked may have issues that make our life a challenge (for some of us we have enough on our plate without that extra!), well there is a way to stay with our chosen partner without taking on their stuff as well.

For me, I have to be mindful of the situation as it comes up and just monitor my own emotions. When my partner is having a PTSD issue, I am able to remind myself that it is not MY ptsd issue right then. It can easily become one if I don't watch it though. So I will emotionally withdraw a little bit and will view my partner as only a friend or even as just someone I know. I work extra hard to not take the situation or even things said directly to me as personal... even when they are personal. As the years have gone by (11 of them now), I have learned how to know when what is being said is PTSD talking or if it is something personal I have to address with my partner.

Another thing I do is to focus on my own self care. Sometimes I have to get away by myself and do whatever I need to do to bring myself back into balance. For me, that was not easy at first due to a little bit of that possessive nature some partners get. Whenever I have a need that I must fulfill for myself, I have to just draw a line and make a stand. Sometimes that means I can not sit around and listen to a PTSD driven blow-up because it is making me upset, so I will excuse myself. My partner does not like it, but we both know that I will be back when the situation is less volitile and safer for both of us.

Being able to understand your true needs in order to stay safe is vital.
Being able to articulate those needs to your spouse will help you both be able to maintain the relationship in a healthy way.