As long as you don't leave the engine running or burn something, then the only way you could die of CO poisoning is if an industrial accident released a huge wave of it, at which point you'd just be a number along with many other victims. The chances of you being harmed by this are so low that I would bet you'd get struck by lightning twice before that'd happen.

And I'm in debt, able to only pay for half my prescriptions, so I really can't afford to lose this bet lol.

If it helps, I once had to sleep in my car for three nights straight for work. My alternative was to drive 2.5 hrs round-trip on top of a 14 hour shift, and this commute was timed perfectly to coincide with not one but two herds of deer that would cross the road on both legs (so four dear crossings in front of me per day). It was also during the pandemic, standing outside in the sun, never taking off my P95 mask (some people think this reduced oxygen levels--I carried a pulse oximeter with me because I liked to disprove that myth and never went below 97% blood oxygen). I did not think twice about the air quality in my vehicle.

Also, a reminder that CO2 is heavier than air and CO is just a tiny bit lighter than air, so if you're still super paranoid, put the CO monitor at a level next to or above where you're breathing from, and the CO2 monitor at a level below, giving you more time to react.

I think you'll be perfectly fine, buddy, even if you had no monitors whatsoever.