(Adding on, not disputing.)
If cooking meals in that situation, I'd suggest using a camp stove outside at parks and for lunch. The more you look like everything is under control, the less police will focus on you. Flip the norms and eat something that doesn't require cooking at night (less clean up in the dark, etc) like a sandwich.
If you're not going to be in the car long term, buy fresh to cook or stash things you can keep in a cool bag or that are shelf stable. You can't justify a 12v fridge and battery, and buying ice for a cooler is annoying and adds up. No shame in tins or whatever else if it's all short term.
Eat and do any other sleep prep in one place, then drive to your likely overnight spot and do little more than move to the back and go to sleep. Minimise your visibility in that "person about to sleep in their car" phase. Look for spots near mid-range apartment blocks where residents don't keep track of exactly which car belongs to who and won't call police because they're suspicious. The police are mostly looking for people creating visible trouble (belongings spilling out of vehicle, pissing everywhere, yelling) or because residents have called to get you moved on.
I said in another comment, but ultimately the desktop computer is the major hindrance. Get even a simple laptop and you can study/work from a library or park and improve the employment situation as a priority. Others have given tips for options there.