One more thing that might help, which helped me....
I had to make a note to myself not to yell at him as a note on my cell phone so that every time I look at it, it would remind me. Find somethign that would work for you. :-)
I also sat down with him one time and talked about how mom didn't want to scream at him so much and that I was willing to work on that, and asked him what could he do as well to make things better (such as listening without arguing)... kind of like a little verbal contract, and I saw his effort to do better (as long as it was under his control). Lots of positive reinforcement also on those time when I catched him actually not arguing where he otherwise would try to make a case. Hope this helps.
