Is the questioner obligated to return the money that was stolen from her and that was designated for her family to her husband from her own private money, or do her family bear that responsibility?

It is impermissible to deposit money in the Post Office and receive the usurious interest accrued from it. Your family must repent and dispose of the usurious interest by spending it on the welfare of Muslims or on the poor and needy. It is forbidden for you to assist them in this, due to what was reported from the Prophet, peace and blessings be upon him, regarding the curse upon the one who consumes usury, its giver, its scribe, and its two witnesses. This indicates the prohibition of assisting in falsehood. You must advise your family to repent and to repent for assisting them. As for the money that was stolen from you: if you were an agent for your family in borrowing from your husband, then you are not liable for it except in cases of negligence or transgression, and your family is liable. If you were not an agent, then you are liable for the money to your husband, unless he agrees to waive his right.