Is it permissible for the husband to give his father zakat on his money if the father is in debt, has limited income, and does not find enough to cover his expenses and debts?

It is permissible for your husband to pay the zakat of his wealth to your father if your father's income is insufficient for his usual expenses and to pay off his debt, as he is deserving of zakat due to his poverty and indebtedness. A person may combine characteristics for which he is eligible for zakat, such as being poor and indebted, in which case he is given [zakat] for his poverty and for his indebtedness.