Are children to blame for their father borrowing with usury and his refusal to repent from it, and what is the way to convince him to rid himself of usury, given that he mistreats them because of this issue?

Usury is a grave sin. Those who take out a loan with it do not burden their family with sin unless the family approves and assists. Otherwise, there is no sin upon them, as Allah Almighty says: (And no bearer of burdens will bear the burden of another). Your sorrow over your father's sin is commendable, but contemplating suicide is reprehensible because it brings no benefit and repels no harm, and it may lead to weakness of heart. Suicide is a grave sin; rather, one must be patient, seek reward from Allah, supplicate, and be optimistic, because Allah expiates sins through worries and calamities. Do not despair of the mercy of Allah.