With additional clothing or a liner, they can go lower. The bag uses synthetic fill of Hollofil, Quallofil or Polarguard . Down is light weight, stuffs into a small shape, is expensive and has great insulating qualities, but diasterous ones when wet. Further, once wet, it is heavy and hard to dry. Leave down to the experienced crowd.
Synthetic fill is more forgiving for newbie crewbies.
Most synthetic bags wash and dry easily. It fits your build. My sister's family takes an interesting low cost approach. They fold over and zipper Polartec blankets for mild camping. It works, is washable and inexpensive.