It sounds like there maybe be more than ADHD going on with him. While adult ADHD can present with irritability, out right physical harm and extreme anger are not common with ADHD alone....at least that I have never seen (7 years working in mental health now). I would strongly urge him to go back on the Strattera or maybe try something different. And if you catch him in a really good mood talk to him about maybe going to therapy. It sounds like he could use it.

And if things turn physical LEAVE HIM IMMEDIATELY!!!! I know it is a hard thing to do but you do not deserve to be a punching bag!