I was forced repeatedly during an abusive marriage to perform sexually. If I did not comply, my ex threatened to hurt our children, which he carried out too many times. Is this not rape and prosecutable?

It could be considered rape and whether its prosecutable would be up to a prosecutor to determine. I would certainly suggest you contact your local district attorney or prosecutor.

While it should be, his defense attorney would merely say it never happened, do you have it on tape or video happening ? I will assume no one else has heard him say this ?

Also his defense attorney will ask, if it was why after the first time did you not take the children and leave.

And that is also my question, once is bad, but to stay knowing it is going to happen,

When you are in an abusive relationship, you lose all self esteem and are isolated. I was a disabled mother of 5 with no extended family to help and no where to go. I did the best I could at the time. It's not like I didn't call the police, tell my doctor and went for counseling. You eventually come to a point where you make a decision to accept it or break]free. No one should judge a person in an abusive relationship, as they could never understand the horror of it unless they experienced it.