Does the remaining amount owed by me for the period of my imprisonment fall due, or am I obligated to pay it?

It is impermissible to take money from relatives who appointed you to make purchases; this is an aggression and a betrayal of trust, based on the Almighty's saying: "O you who have believed, do not betray Allah and the Messenger or betray your trusts while you know [the consequence]." You must seek forgiveness and return the money to its rightful owners, and imprisonment does not waive this right.