Is it permissible to travel using money derived from usurious (unlawful) interest to visit ill and elderly parents, especially when there is a debt that prevents one from traveling?

It is permissible for your husband to give you money from ill-gotten gains to maintain ties with your father and visit him, if you are poor and do not possess enough for that purpose, similar to what is permissible to give to a wayfarer. A poor person is one who does not possess what suffices for their essential needs. This is with the caveat that it is not permissible to deposit money in usurious banks except out of extreme necessity, and it is obligatory to dispose of usurious gains by spending them on the welfare of Muslims and the poor.