CO2 is a harmless NATURAL gas in the atmosphere

There is somewhat of a balance between the CO2 taken up (during photosynthesis) and the CO2 expelled (during respiration, as occurs in the nearly 7 billion humans you describe).

Every sugar you eat required 6 CO2s from the atmosphere to produce it and it will release 6CO2s back to the atmosphere when you metabolize it.

The same holds true for your heat question, in that the energy humans release isn’t magically created by them, but instead came from the food molecules (stored solar energy) they metabolized.

The problem is not the normal flow of energy and CO2 on earth, instead it's the fossil fuels (e.g. the billions and billions of tons of sugars that have not been metabolized, and instead have been sequestered in the earth for over a hundred million years and have only VERY RECENTLY been combusted at high rates by human activities. This fossil source of CO2 would still be safely locked in the earth had humans not used them for fuels, thus releasing them into the atmosphere where they are contributing to an increasingly warming of the earth's surface where we live.

There has been a measured and very significant increase in atmospheric CO2 in the last two hundred years corresponding to increasingly warm earth surface temperatures.