Protein
per day.

Between 1.6 and 2.2 g per kg of body weight. Morton's meta-analysis (2018) pinpoints around 1.6 g/kg as the point beyond which the benefits for mass slow down, with a useful margin up to ~2.2 g/kg.

Yes: in a calorie deficit it's worth raising it (toward 2.2 g/kg or a little more) to protect muscle mass while you lose fat.

For healthy people, high intakes (up to ~2.2 g/kg and beyond) are considered safe by the research. With kidney issues or other conditions, ask your doctor.

Spreading it across 3-4 meals of ~0.4 g/kg helps you make the most of protein synthesis throughout the day, but the daily total remains the most important thing.