Don't call yourself a fool, just don't lie to yourself either. We've all been there! And we've all felt foolish, but we must be gentle with ourselves. I don't know anyone who hasn't made the same mistake and been in the same situation you describe, myself included, multiple times... However, you need to learn right now that that even with PTSD, there is not any excuse whatsoever for his behavior! You are manipulating yourself by even suggesting that, and you are creating excuses for an abusive partner. He's an adult, and so are you. He can either seek specific treatment, now*, to tackle this ridiculous abandonment issue, or the relationship can end, now*. He needs to take responsibility. No excuses. And by the way, prepare for this to never occur - because he's not a poster child for PTSD, he's a poster child for emotionally unavailable men. And these people are rarely adult enough to take real responsibility and create real change in themselves. Meanwhile there are good men out there who will be more than eager to text you back under any circumstance, mental illness or not!
You can find yourself 100,000 other people with PTSD of all degrees, who will never let a whopping two weeks go by without a text message response to you. You can find people half your age with PTSD who would never do this. This is beyond unacceptable. It's up to you to set these boundaries. If you let this slide you are at fault for allowing yourself to be treated this way without repercussions, and he will continue to do this over time. However, the fact his behavior is already so flagrant lets me know, even if I had not read any other part of your post, that little allowances have become bigger and bigger over time. So I can infer that the entire dynamic of the "relationship" does not fit a healthy relationship model. If he had behaved like an adult instead of like a teenage child, he would have flat out told you that he needed space and did not want to speak/text for 2+ weeks instead of leaving you in the dust.
You know who I don't text back? My abuser. Why? Because I don't have any respect for him, because he has none for me. Notice how profound the lack of respect has to be for a person to not respond to you for 2 weeks, and this person claims to be in a relationship with you?! Insanity. Denial. Lies. Manipulation. Abuse <<<< The more you think about, these words apply to the situation. PTSD is not an excuse. A person with PTSD can choose to learn about themselves, learn new coping strategies, and take responsibility for managing their behaviors. If they are not ready for a relationship then they need to stay out of them. Your partner is not relationship material at this time, and may never be. Don't worry about him. He clearly is not worried about you. Do you really think someone who is capable of loving you would simply stop texting you with no explanation, meanwhile posting stuff online about there other accomplishments! Talk about red flag, this is a clear flagrant foul, a total violation of all things "love" and "respect". You can only control yourself, and unless settling for this kind of treatment the rest of your life is the best you think you can achieve, I suggest you end this thing now. And I get the feeling you know you deserve 100X better.