Since under normal conditions protein isn't used for energy, should protein be counted as calories?
Under normal circumstances protein IS used for energy.
Eat insufficient program grams, and the body will burn that many grams of protein anyways. it will burn lean to make up for the deficit.
Eat any protein grams in excess of your metabolic need and the body has no storage mechanism for protein other than extremely slow growth of lean. The rest is burned for fuel. About half the calories burn directly for energy, 2 calories per gram. About half the calories are converted to glucose, 2 calories per gram. Excess dietary protein equals a slow source of glucose.
Your example is an *extremely* low protein one. Only 50 grams of protein. The only westerner who would eat that little protein is a wannabe vegan who has no clue abut nutrition so they eat nothing but veggies.
The usual formula is 0.8 grams of protein per pound of lean body mass. Most people eat twice that many protein grams.