As messy as this current situation is, for people who keep bringing up divorce seem to overlook that all that would really accomplish is making a bigger mess where everyone is miserable. No one would benefit at all, and it would be worse for Hazuki than anyone else, caught between the parent who actually raised her but can’t financially support her, and the absentee parent who can financially support, but neglects all her other needs (the same way he treated his wife). Nest case scenario, she goes to live with other relatives while her father pays child support and rarely ever visits, if at all.
I don‘t see any reason not to keep the status quo going, for now. At least until Hinata and Hazuki graduate. However, I would have advise Mizuki to start working on her exit strategy.