Bubbles,

Your best bet is to use Tough Love with Shawn.
If, he steals from you press charges, if he threatens you press charges. When he threatens the other kids at school...have the school press charges.
If, your afraid for your life and he has threatened you..press charges, have them haul him away to juvenile hall, a mental facility, etc. wherever.
When you press charges against him a court date will be set. When you get in front of the judge tell him about his behavior at home, school, etc.
Court will see to it that therapy, medicine, etc. is mandatory for him.

My son was just about the same way at the age of 14.
All of us were scared, of his antics, his treats of suicide and hurting others.

If, you let him get by with all of this it will only get worse.
Any threat...large or small call the police have them come out. If, you are afraid for you life have them haul him off.
The longer he gets away with it, the worse it gets.
You will be showing Shawn how much you care about him by calling. He just doesn't know it right now.

Make your husband see this! It's the only way.
Get the court behind you.