The system considers household income. If both parents are working more of the stepparent’s income could be used for household expenses which would free up some of the parent’s income for school. If stepparents don’t want to contribute for a member of their own family, why should taxpayers?
You have bigger issues than college funding. Have you tried family counseling? It might help. I don’t know why you thought it was necessary to point out that your wife wasn’t married to her children’s dad. Why does it matter? Do you think there’s negativity regarding her mother that your daughter has picked up on or has she always had an attitude towards you?