I say, and with God's help: The original rule is that if the husband is in debt, he is not required to pay Zakat al-Fitr. Therefore, Zakat al-Fitr is not obligatory for him if he does not own the equivalent of (100) grams of gold. Even if he is wealthy and his wife gives it on his behalf as a donation, it is permissible; as there is customary permission. And God knows best.