Will I be sinful for working in a usurious bank, knowing that I have not found another job for a full year, and I have family obligations and debts?

The basic principle is that working in usurious banks is forbidden, due to the cooperation in sin involved. However, it is permissible for someone in dire necessity to work there if they cannot find what to spend on themselves and those they support, with the obligation to diligently search for permissible work. It is forbidden for them to remain in the forbidden work once they find permissible work.