Already these boards have been helping me tremendously with communication in my relationship. I have changed my responses when he spirals and it is really helping. Fights are less scary an end more quickly. 
Hi, I'm new here too and I believe we live the same life...  My relationship went on a lot longer though before I came across a more solid reason for his behavior.  I just thought it was immaturity or something that we could evolve out of.  I could envision our future together.
What exactly did you do as far as changing your responses?  I may have missed the boat on this one as after our last argument - one sided, as I figured out I should just stay quiet - he has not called me for a week now.  Sometimes he'd disappear like this after the argument and I never knew if he was gone for good or not so I have no idea what our status is.  
But if we continue the relationship, I'd like to know what people did that helped.