It has got to be pretty difficult for you right now.  Therapy only works when the patient wants to change their behavior.  Your son needs to be diagnosed by a competent psychiatrist.  Depression does not ordinarily lead to violence.  Therapists and counselors are not medical doctors.  My suggestion is that you pre-screen before you bring him in.  Take your documentation and talk to the psychiatrist alone first.  Accomplishes two things:  you and the psychiatrist already have an understanding before you bring him in and you don't have to worry about him misbehaving or interrupting while you are trying to get your point across.  Additonally, you can rule out other disorders.  Your husband wants you to take him to a doctor, so he should be amenable.  There is no cure for a psychopath...but if he has a mood disorder, the right medication can help.  May have to try several or combinations thereof before you get results.

     I don't care what his problem his.  ANY violence toward you is unacceptable.  It will escalate is steps are not taken now.  Regardless of his motivation, he can control his behavior since he doesn't act out around your husband. 

     Depending on the diagnosis, there is probably a parent's support group you can join.  Being able to unload and get advice from those who have been there is invaluable...especially if you and your husband are at odds.  Hope this helps.