I think you are in a real down at the moment ScaredofLonely and that is bringing on these really negative thoughts.
I go through it myself but I have kids, I cannot go there where I feel guilty because the burden I am putting on them. All I can do is the best I can to work through my issues and push myself to be the best mother possible. My kids love me, your partner loves you. You try your best and don't go into the guilt cycle, that is a guarantee to pull yourself down and your partner and lead you into hurting them. Having said that you can't be perfect, there are times when your partner will suffer because of this condition, but they take the good with the bad. That is true for all relationships.
Imagine it were the other way round and, say you were partner to someone with a physical disability. If that person felt guilty because of their physical disability because it burdens you with all the extra things you might have to do how would you feel? You are with that person you know they have a physical disability and you love them and look after them it is your choice. There are millions of couples where one partner has a physical disability or mental disability out there and they work through it because that is what people do. No-one is perfect not even in relationships where there is no physical or mental disability.
Yes this PTSD is horrible and there are really bad days, but it also gives you an insight into life and a compassion for others and a knowledge of suffering that makes you someone special who is worth loving. Someone who loves you will know you have times when you need your space. Everyone needs their space even those without PTSD.
There is continous pain in life and relationships whether it be due to PTSD or other problems that make up life. Life is not easy, relationships are not easy but as long as you show respect for each other and love each other and work at doing the best you can then that is all you can do.
Please, don't compare PTSD with abuse. It is not the same. It is not a deal breaker. I have been in an abusive relationship, it is not the same.
The supporters on here are writing and venting their pain but I read most of them as really valuing and loving their partners and taking the good with the bad. A lot of what you read on here is others venting and getting support from other supporters who understand. Part of PTSD is needing space, that is not something to feel guilty about as long as it is balanced. That is my feeling on this, but maybe you should ask some of the supporters whose stories you are reading?
You cannot know if you are holding someone back from better things. You probably are the best thing in their life you just don't know it because you are focusing on all the negatives. You have good qualities, write them down and understand why your partner is with you despite some of the crap. Focus on your good.