How should I act if my father asks me for a loan to be repaid from project profits, and my husband refuses this and threatens divorce?

A woman is not permitted to take a loan for her father if her husband refuses, especially if it will cause her harm. This is particularly true since her borrowing might lead to harm if the loan is not repaid; she could be imprisoned, and her husband might be forced to pay to free her, causing him psychological and material damage. However, if the loan involves usury (riba), it is forbidden for her to borrow, even if her husband agrees, because there is no obedience to a creature in disobedience to the Creator.

It is advisable to gently persuade the husband about the importance of honoring and helping parents. If he gives permission, it is permissible; if he refuses, it is not permissible.