Others haven't already pointed out that you're mistaken regarding "an insanely large portion of the CO2 is simply us and our livestock breathing." But also, consider this:
The carbon in the CO2 that you breath out comes from the carbon that you consume. That carbon - by virtue of its state - is part of an equilibrium carbon cycle that makes our planet habitable. I.e. the apple tree consumed CO2 from the atmosphere to create the apple that you ate, and you returned back to the atmosphere the carbon that the tree previously consumed.
Now consider the carbon that has been isolated from the cycle over billions of years as the planet became habitable to creatures such as ourselves and our non-human friends. That carbon is in the form of coal, oil, etc. If we leave that stuff in the ground we retain the current carbon equilibrium. If we burn it, we change the equilibrium by taking sequestered carbon from the ground that was "locked away" and add it to the atmospheric carbon cycle.
Yes, and I am considering moving more in that direction. I've actually quite enjoyed specifying and implementing safety-critical PLC software in my new career. But I'd really like to invest more time in formal specification and verification, particularly in embedded software!
I worked in software for 15 years after graduating B.Sc. engineering (electrical). As a software engineer, I Worked in pharma, aerospace, heavy industry (mining), logistics and some general web development as well. I got so fed up with the industry BS; tool churn for tool churn's sake, brogrammer culture, etc. Particularly sick of BS mantras like "move fast and break things"; the attitude that technology is necessarily a force for good, because... well... its technology. Silicon valley "solving" non-existent or BS problems.
So I took a huge pay cut to go works as an electrical and control systems engineer (zero experience). I love every minute. After 5 years I've significantly overtaken my tech salary and I'm solving real problems for real people instead of the bullshit work that is 90% of software "engineering".
Although probably not the majority, many experimental aircraft do use car engines. I'm building a Zenith 750 kit aircraft and installing an engine from a company called Aeromomentum who convert Suzuki engines for use in light aircraft. The model I have installed is a 117HP engine originally designed for use as boat outboard motor. A sibling comment mentions that car engines aren't designed to operate continuously at high power. Outboards are. And there are benefits to using highly developed and tested engines vs traditional aircraft engines - efficiency being the most obvious.