I am really impressed and inspired by your desire to find forgiveness for your mother.
It was not until I turned 39 that I realized that my carrying anger towards my mom for very similar things as you described was only helping to further HER story; her sense of being a victim.
As long as I carried anger in my heart towards her, she could play the victim of my anger. It didn't matter how justified the anger was; she just continued playing her role in her life, which is to be the victim.
I chose to let go of the anger and have been working on letting go of it since. Forgiveness is a major part of that.
Kudos to you dude. Keep going.