Short answers, pulled from the story.
Humans must obtain nine essential amino acids from their diet including phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine. These specific amino acids cannot be synthesized by adults and are required to prevent death from protein-energy malnutrition.
Women ages 19 to 70 need to consume 46 grams of protein per day while men in that age range require 56 grams daily. These Recommended Dietary Allowances were calculated based on 0.8 grams of protein per kilogram body weight using average weights of 57 kg for women and 70 kg for men.
The Kjeldahl method and the Dumas method determine the total nitrogen in a sample to calculate crude protein content. The Kjeldahl test is typically used because it is the method the AOAC International has adopted for this purpose.
Plant protein foods contribute over 60% of the per capita supply of protein on a worldwide basis. In contrast animal-derived foods contribute about 70% of protein sources in North America.
The FAO proposed changing to Digestible Indispensable Amino Acid Score in 2013 as an update to the Protein Digestibility Corrected Amino Acids Score. The PDCAAS rating was previously adopted by the US Food and Drug Administration and the FAO/WHO in 1993 as the preferred best method to determine protein quality.