How can I get through?

I have been married for 19 years and have three wonderful daughters (18, 12, & 5.)  My wife and I both come from somewhat challenging childhoods.  My mom past away when I was four and my father (without us knowing) lived to lives with two different homes.  In her case she grew up with a very strict, intimidating, macho of a dad that used to hit the kids and his wife quite a bit.  When we met she was pregnant and abandoned by the child's father (my daughter now.)  From the begining we had issues with how she dealt with things and an obvious anger she developed through her life that resided within her and it was very destructive, offensive, painfull, and cruel when it came out.  I always thought that she would change, I always prayed for her to change.  We have had good times and tough ones, but her lack of respect and psychological abuse that turned into physical on a few occasions made me realize that she either did not want to change or could not for some reason.  Back in 2006 I went to my country for my 25th year anniversary, my high school reunion.  I got a chance to talk to my family and friends (a priest included.)  They all agreed on something that I had not seen; they agreed that we got together and married out of need and not love.  She needed a man to help her raise her child and I needed a woman and a child to form the family I never had.  That same idea was later re-affirmed by a marriage counselor.  When I came back I asked for a separation but because of her pain, promises, and even threat of abandoning the family, I decided to give her a second chance.  Eight monghts later, we were in the same situation.  Although physical abuse had subsided the psychological did not.  I asked for a separation again.  Again she cried, promised to change, told me that I was breaking our family because I came from a broken home.  She even threaten to drive her truck into a wall; what I don't know is if she thought of doing that with the kids or not.  She agreed to go to a marriage counselor.  The doctor made us realize that she was a victim of her past experiences.  She had seen her dad abuse them and her mother and without thinking and realizing she asumed the role of her father and did not want to be the weak one like her mother.  The fact that whe was left and abandoned when she was pregnant only exacerbated all the anger she had trapped inside of her.  I however could not expose everything I wanted to the doctor because he had given us as part of his disclaimer that if at any point we talked about physical abuse he was supposed to report it to the authorities.  I wanted to help my wife not put her in any trouble with the law.  We stopped going.   Our relationship took a turn for the worse due to the economy.   I worked in the mortgage industry as a wholesale banker of subprime loans.  As submissions subsided as well as my pay, the company was forced to close down.  I was unemployed!  I have been actively looking for work and it is not easy to find something that would help us pay for our mortgage; we sold our house.  Unfortunately we did not make enough to pay off all of our debt.  That brought more misunderstanding, abuse, insults, disrespect, and humiliation to our relationship.  Two weeks ago I was once more insulted in front of my kids and said no more.  The next week I asked her for a Divorce.  I don't want my kids to grow and have their lifes affected by their parent's bad relationship; like in her case and maybe mine too.  She cried, cried, admitted to her mistakes, promised to change (again), she even admitted that if she had been in my shoes she would have left a long time ago.  She says that she is not going to give me the divorce, that I am the man she wants to grow old with.  She says that if I leave her, she will hate me, and I don't want that.  I don't share the same feelings, I haven't for some time.  She will not let me go.  How can I make her understand that our kids should come first?  That I am not going to abandon them?  That she is always going to have my support and friendship also if she wants?  I made up my mind but she won't accept it.