How should the remaining savings for our needs be distributed between my mother, my brother, and me after my father's passing, considering that my brother has only recently started working and my salary is unstable?

If the money is shared among you and it is difficult to determine each person's share, it is best to seek reconciliation and distribute it fairly while considering forgiveness if someone has taken more than their rightful share. The Prophet ﷺ recommended fairness in division, resorting to drawing lots if needed, and ensuring mutual absolution and understanding.