I was given a copy of the "Prayer for a Troubled Marriage" ... at the bottom of the page there is a reference to The Weapons of Our Warfare Volume 1, Kenneth Scott, Spiritual Warfare Ministries ...
I have been watching your question, and I noticed that you have not received an answer yet. I don't have the correct answer either. I do however have an answer. My marriage was in trouble once, so I can relate to where you are coming from. After 29 years of marriage, my husband decided he did not want to be married anymore. I didn't have a prayer for a troubled marriage but I did know how to go directly to the throne of grace. Being a child of God, I had the right to do so. From my own heart, I told God the inner most thoughts of my heart. I talked to him as if he was a friend sitting directly in front of me. I didn't use any fancy words but I poured out my heart to him.
I am glad to say that he turned things around. He did what nobody else was able to do. I am happy to report that me and my husband just celebrated our 36th anniversary and all is well.
If you do not get your answer, try talking with him directly. He likes that more than anything.
Be Blessed and good luck.