Re: he's on the brink, i don't want to lose him.
From reading your post I get the overall sense that he feels he has no control in the relationship. It doesnt necessarily mean its true, but he is feeling powerless. He feels that you will do or say whatever you want, and if he reacts or expresses his feelings you will throw it back in his face.
I imagine he feels you do not validate his feelings or respect his position.
I used to be a "my way or the highway" kind of girl, until I realized how my (now ex) felt like his opinions and concerns never mattered. Becasue I was always batting them off with a reason or an excuse as to why I was allowed to act like that.
Regardless of whether you feel justified or "right", when discussing someones issues with you, its is best to actively LISTEN. Really HEAR them, and try to understand their point of view. Tell them you understand why they feel that way and try to see your role in the issue.
It doesnt mean you have to roll over and play the door mat. By all means you should also speak your mind, but you can do without throwing it back in his face. "Well you did this so I did this" is not a good way to solve a problem.
If one person in a relationship feels thay are not being "heard" and taken seriously, they begin to feel powerless and resentment. You can avoid making him feel that way by listening anf thinking before you react to what he has to say. His feelings are real and they are truth to him, so try and respect that (even if you dont agree). He should also do the same for you. It is about mutual respect and communication.