No disputing your numbers but you are confusing quantity with quality.

The goal of humans should not be to determine the maximum population the earth can sustain. The goal should be to maximize the quality of life of each individual. Yes, that will require more energy consumption per person, just as historically the human species invests more energy per offspring than other species via one child at a time, not a litter of 10.

The human species needs to come to grips that we can't sustain an ever expanding population and still retain the essence of what makes us human. The key is to think multi generational into the future, not fixate only on the current generation.

Much better to have fully activated humans at low population for centuries than an enormous population barely surviving that dies off in a few generations. The first case actually allows for more total humans to inhabit the Earth, they just do it over many, many generations rather than all at once just before the resources run out.

Only the numerator is talked about because oil consumption does not match population very much.

Germany has 82 million people, and uses 2.6Mbbl/day.

India has 1,100 million people, and uses 2.5Mbbl/day.

So your hypothesis is that if the populations of those areas were doubled - no significant increase in oil consumption - if the population of those areas were halved - no significant decrease in oil consumption? You feel oil consumption does not change with changes in population?

So it has 13 times the population, but uses slightly less oil.

The rate at which various populations use oil is separate from whether or not they use more or less if their population grows or declines.

Greenhouse gas emissions are much the same.

Germany produces 838Mt of CO2e. India, 1,0080Mt CO2e. 13 times the people, but only 20% more emissions.

It's good to know that India has volunteered to maintain a much smaller amount of C02 emission from now until eternity.

Imagine that there are two houses along a street. One has one European middle-classed guy in it, he puts out 8 rubbish bins every week. The next house has 13 people in it, all south Asian and working class, except for one middle-classed person, the boy they could afford to send to university, they put out 10 rubbish bins.

The rubbish collector tells the street, "there are too many for us to collect, you need to reduce to just 1 rubbish bin each on average. There are 203 houses on this street, I don't care if it's one house with 203 bins or 100 with 2 bins each and 3 between the other 103, or what. Just get the average down."

The European says, "Tell those darkies next door should stop having so many babies. That'll sort it out."

Imagine there are two houses along a street. One has 35 Indians living in it and they are adding 1 more every 6 months. The other has 4 English living in it and they are at a stable household level. The English tell the Indians they should stop adding to their household size. Some American steps in and declares that the English have no right making suggestions to the Indians since they throw out so much more trash. Then he sanctimoniously adds that his household has been increasing in size for decades as well, and save for the lack of space, long lines, and limited resources, it hasn't been a problem.