YesBut.
I do not mean this to be hurtful, although it is not going to sound good. I have been guilty of the same thing myself, and it's a mistake a lot of women make besides you and me.
You are not a useless coward. You are neither useless or a coward. What you are is someone who is fooling herself that you have even the smallest bit of control over the situation. You have convinced yourself that sleeping on the windowsill will protect you from rape. You have convinced yourself that not making waves will spare you from dealing with any kind of ruckus your H wants to create. You have convinced yourself that you are responsible for the quality of the relationship between the DCs and their father.
You have adopted a coping mechanism, as many women do, because if you were to allow yourself to see the thinness of the thread by which you are hanging, and the children too, it would paralyse you with terror.
You are as free from immediate danger as he chooses to allow. You can do or say nothing to diminish the threat he poses to you, or increase the threat he poses to you. He does as he pleases, and he will do it without regard to your behaviour or your words. You have absolutely no control or influence over the situation. You are living on a leash.
This may seem stark, and I hope I have not been brutal. You need to go to WA or Refuge and start to build up your self again, start to trust your own perceptions, and start feeling on your own behalf again.
xxxx