I know exactly what you mean. I hate it when my daughter receives the short end of the stick because her dad has other priorities.
My only hope is that I can be healthy enough to give her the skills to deal with her life in a healthy manner.
In the moment of the disappointment, I am not sure what to do. I don't make excuses for him, but I often say that he is "busy". I don't want my daughter to think that his behavior is in any way her fault. I really want her to feel like she is important to him, but I cannot make him show her that. So, I am trying to give my daughter a lot of contact with the people in my family and life who do show her she is important.
Keep up the great work, your progress will definitely positively affect your girls.