Sometimes drugs mask issues that are deeper than the drugs. This often results in the true symptoms remaining as the drugs leave the system. It is very common for people with drug habits to experience true symptoms such as a mood disorder or anxiety issues. That could be why he is still abusive. He needs to see a mental health professional so that his mood is more typical and he can stabilize the deeper issue. Reactions to drugs do not last for extensive periods of time. Encourage him to see a professional so that he can address the real problem. Now that the drugs are in the past this behavior is indicative of a mental health problem - possibly a mood disorder. People use drugs to fix an issue like this and really just postpone experiencing the uncomfortable presence of these problems. Find a professional in your area.