Please get yourself somewhere where you feel safe Girlio. Do you have family or friends you could stay with for a week or two while you get legal council and perhaps a restraining order? There are also women's shelters and retreats that are specifically for women in your situation. Because of the threat to your life (and by the way, if he considered, planned, and even attempted to kill you once and he "doesn't know why," there is NO garuntee that he won't be inexplicably triggered into that homicidal mania again) I really fear for your safety and well being. You are in a pretty extreme abuse- based relationship and you have to take equally "extreme" measures to protect yourself. You mentioned a stepson? Is he a witness to this abuse and rape? Think about how witnessing this kind of male behavior in a relationship might ultimately influence his development into a young man? Think of what he would go through if you were killed. If you can't see yourself as worth saving, see your stepson as worthy of having you, safe and alive and still in his life.
I feel such pain for you in your situation. I wish you the best and send all the strength I have to you. Do the right thing.