Yes, copper is as vital as calcium, iron and zinc. An adult needs 0.9mg of copper every day to maintian good health. Nuts, seafood, wholegrain cereas and offal are good sources of copper and a balanced diet should provide adequate copper.
Yes, it has been used for many years. However the nitrous oxide fumes given off when absorbed into surrounding fabric create a fire hazard. Also energy is used in the heating process. Better to patinate cold or use prepatinated copper.
Gunmetal or dezincification resistant brass.
No. Copper is not susceptible to precipitation hardening.