Anger and distancing are all common parts of PTSD. PTSD is an anxiety disorder, so sometimes, all that anxiety from outside sources can get placed onto you.
Say, for example, that his PTSD symptoms are particularly bad and then his boss writes him up at work, his car won't start on the way home, and his mother calls him and stresses him out. Then when he gets home to you, you forgot to pick up his clothes from the dry cleaners, and BOOM - it just caused world war III. Sometimes, anger gets misplaced and doesn't seem proportionate to the thing you did. You're getting broken up with or yelled at for minor little things. At least this was my experience. It's not your fault and you have know this. And your partner has to recognize this, also. The fights and distancing aren't your fault.
The best thing you can do is to give him his space when he asks for it. If he's continuing to check on you, that's a really good sign. Try not to feel overwhelmed and just remind him you love him and are there for him. Learning the symptoms and how to cope with them and what they really mean is crucial. I encourage you to just look over this forum and just read as much information about PTSD and its symptoms as you can. The more you know, the better off you'll be.