I'm not bothered in the slightest about the financial burden to the tax payer, despite being a high rate one. We waste billions on far less important stuff than feeding and housing children who have no choice in being born.
I do think though, 7 kids, the older of which has had 3 'stepfathers', at least the last 2 of which have been abusive, shows a pattern of an extremely irresponsible and selfish parenting where romantic relationships have been more important that your children's wellbeing and welfare. None of these children have any of their 4 fathers or their father's families in their lives as positive contributions.
Your kids had no choice in all these men being in their life and your basic duty as a parent is to protect your children and keep them safe. Your 2nd abusive relationship involved rape and you have teenage daughters. I dread to think what your son and older daughters have been exposed to.
Sorry but having gone through similar myself growing up with 7 siblings from 3 absent fathers with domestic violence, poverty, neglect and abuse (some of which she didn't notice despite it taking place under her roof). She cut contact with each father's family as well so no grandparents, aunts, cousins, etc. I always idolised and defended my mother as this amazing woman who worked so hard (unemployed) to raise so many kids, until I had my own kids and the scales fell from my eyes.
Have you thought about family therapy?