Does the حرمة fall upon the mother or the father, and what is the solution for a situation in which the father barely spends on the mother, and he has expelled her and her two daughters after threatening them with a knife, in addition to having an illegitimate relationship with another woman?

If a husband's beating and expelling his wife is unjust and forbidden, then Allah Almighty says: (Then if they obey you, do not seek a way against them. Indeed, Allah is ever Exalted, Most Great). As for the ruling on the wife's sin for refusing to apologize, it cannot be definitively determined. The solution is to send two arbitrators, one from his family and one from hers, to reconcile them, in accordance with His Almighty saying: (And if you fear dissension between the two, send an arbitrator from his people and an arbitrator from her people. If they both desire reconciliation, Allah will cause agreement between them). If reconciliation through the two arbitrators is not possible, they should resort to the judiciary to do justice to the wronged party.