Is the questioner obligated to give his brother the amount he previously promised him, despite the brother's misconduct and his causing of family disputes, or should he spend it on charitable causes for his deceased father? And if giving it is obligatory, when should that be, given that the questioner is awaiting a job and has other debts?

You must repay the debt owed to your father, as it is an inheritance that should be divided among the heirs. It is commendable to fulfill your promise to your brother, while also having the option to give charity on behalf of your father, which is a form of showing righteousness to him after his death. It is not permissible to accuse your brother of taking your father's money without evidence, as long as he denies it and claims that he spent the money with your father's permission. It is advisable to maintain the bonds of brotherhood.