Once or twice a year is common, or when a major change happens, such as a new loan, a new job, or a big payment. Checking too often can make normal swings look worse than they are.

Yes, because they are assets you own. Some people also track what they can reach without penalty, which is a separate figure.

It is common early on, especially with student loans or a mortgage. Track the trend. A net worth that is rising over time shows that the plan is working.

Yes, at its likely sale value. Subtract any loan balance, since the car loan is a debt.

No. It shows what you own minus what you owe. Cash flow, which is what comes in and goes out each month, is what decides how much you can spend.