I don't think making yourself a floormat would be the way. What I mean is, don't grovel, beg nor plead. Give him space to think. And give yourself space to think. I read in your op that you are working on yourself in therapy?
I would work on calm and saying that you cannot accept his running out on you when the topics get heated. That it's not conducive to a lifetime of marriage. I really don't think this is completely about you as he claims it is. He sounds young and not adept to addressing the challenges before him. You're not the challenge, his inability to not realize that how he says things matters and is the challenge. It was callous. You don't say that to your wife nor husband plain and simple. Then instead of articulating his viewpoint like an adult he storms off and points blame at you.