Some answers are easy. The size of your cash reserve depends entirely on how long it would take to replace your job. If you have a special skill you need more of a reserve even when jobs are plentiful because it takes time to match the jobs with the skills. Computer programming is a good example. There are plenty of programming jobs but finding a good place to work that needs particular skills might take several months.
Most people have a comfort zone in which they feel secure.
Having a cash reserve can also be crucial in a major part of getting a new job, the salary negotiation. If you're on the ragged edge, not having the 'confidence of cash' can cost you thousands that you will never make up. This means bank deposits, bank money market accounts, money market mutual funds, and short term Treasury obligations. Cash does not include common stocks because their value can fluctuate greatly. I'd hold the cash over paying off the car loan.