Hi, I'd like to help you with your question.
It sounds like your son needs immediate attention by a mental health professional. It is important that you try to get him help right away. His attempts to hurt himself and his expressions about not feeling loved and that he is evil is his way of telling you he needs help and that he is desperate.
It is imperative that you get your son to a hospital to be evaluated. If you can, have his doctor back you up with either calling ahead or sending a referral. Also, contact your attorney and find out what legal rights you have. There must be a way to get your son help without having to involve his father for approval.
In general, make sure you are recording in some manner the problems your husband is causing. If it can be proven he is mentally and emotionally harming your children, then you will have more evidence to help your child with. Write down what is said, times, dates, witnesses etc. Keep a log and inform professionals involved in your situation about what is happening.
It is also important that you have your son and the rest of your children see a therapist. It can be family therapy (that you are involved in) or just the kids. But no court in the world should ever deny a child the chance to have therapy, especially in light of what your kids have been through. So if you need to appeal along the legal path, do so.
There is not going to be a easy way to help your son until he has professional help. You can talk with him and be honest about the situation (at a child's level). Tell him frequently that although the adults are having problems, none of what is happening is his fault. He needs to know that someone is on his side and that what he is being told by his father and what is happening in general will be dealt with by you and other adults. It sounds like your son is taking all this in and blaming himself. That needs to be addressed as soon as you can.
I hope this has helped you,