I'm praying that making myself into a better person, she will not want to leave.
Nothing you do will make her want to stay. She will come back if she is ever able to listen to God's voice. You could not change anything about yourself and she would come back because she woke up. You could change everything and become an actual saint and she won't come back because she didn't wake up. She could come back while still hating you because she got very ill or ran out of money.
She won't come back because of something you did, I assure you. The more I changed, the more of a monster my H became. I got cancer during his MLC and that did nothing.
I know it hurts to hear this. It hurt me so much to hear it. And it can go either way. My H got worse, your W might get better and come back. But it won't be rational. It won't be because she saw that you changed. She can't see you right now, as you are or as you were or as you will be. All she can see is her own pain.
In my journey, I got closer and closer to God until I was able to understand that He has a plan for me, even if it's not the one I thought He had. I am slowly healing wounds that pre-dated my H but which led to my allowing so much abuse. I am finding my own self. I accept my circumstances and try to meet God where I am, not where I wish I were.
All you can do is become the man God intends you to be. Everyday, when you pray, offer her to God. Tell her she is His daughter and He needs to take care of her and tell God you don't know what to do with your love because you have nowhere to put it and it's hurting you to have so much love with nowhere to put it. Write her letters you won't give her to get all feelings out. Ask God to align your will with His. Your will is torturing you right now. You are in the desert now. All you can do is walk to the other side of it and realize your will means nothing. Let her walk through it on her own time. Find the manna God leaves for you along the way and thank God for the moments you can still find joy while in the desert.
I believe I will see the bounty of the Lord in the land of the living. Wait for the Lord with courage. Be stouthearted, and wait for the Lord.