Hi Glara.
First of all - hugs. I know you are in a horrible place right now, and from what you've written, it sounds like you feel 'stuck' and can't see your way clear.
Having said that, I think you already have the answer you seek. I think the posts on this thread and others give some excellent advice. Pretty much everyone here has advised you along similar lines - that, based on the information you've given, the most sane and most healthy thing to do right now is let go of him.
But please note: I said 'let go', not 'give up'. They are two very different things. Distancing yourself from him is not necessarily giving up on him. It doesn't have to mean burning bridges.
Is his behaviour borne of his PTSD? I don't think it matters. Really. Only he can answer that question anyway (and maybe even he can't answer it right now). One thing I feel I can say with some surety is that he IS emotionally unavailable. And emotionally unavailable means that he cannot commit to you, BUT importantly it also means that he probably won't let go of you altogether either. Emotionally unavailable usually means that he can't make a decision one way or another, and it's possible that he's going to keep flip-flapping on you, blowing hot and cold, for months, or even years to come. So if you distance yourself, he might well reach out and contact you again. But that doesn't necessarily mean that he still wants a relationship with you. It might mean that he wants to check that you're still around, but still, that's a long way from having a relationship. Have you made a firm decision on what you WILL accept from him? e.g. Is 'just friends' going to be enough for you? And even if you're happy with friendship only, you have a right to expect certain things from him. If he doesn't deliver on any front? Well...
IMO? The best thing you can do - for him and for you - is to focus on working on yourself, and do whatever it takes to get him out of your head (as long as it's not self-destructive). I can relate to a lot of what you've written (minus the suicide thing). I know that feeling of wanting to get inside his head and work out what he's thinking. The reality is though, it's not possible to do that. Not unless he lets you in again and tells you himself.
I know it's easier said than done, but keep trying. I hope the counselling works out, but I also recommend reading everything you can get your hands on topics that will help YOU e.g. regarding relationship advice (pertinent to your situation), anxiety, depression and trust issues. I really don't know if learning more about PTSD will help things. Again, at this point in time, I don't think it really matters whether he's acting like this because of the PTSD or not.
You have every right to feel the way you're feeling. And it's very very important to grieve the loss of your relationship with him. If you don't grieve 'what could have been', you will never be able to fully move on.
You will get there, in time. Remember to be kind to yourself.