Ok, $300-400 makes more sense then $3-4. Do you have all the paperwork concerning the loan? ; it should be pretty clear on how much was borrowed and what the interest rate was.
The one thing I still don't understand is the insurance. How does the car dealer have anything to do with the insurance? I don't see how car insurance can be tied to a fixed payment every month, since it can go up or down depending on your driving record and accident history etc. Even at $429/month; the cost of insuring the car for a year is over $5K a year. That seems like an awful lot of money just for car insurance. Do you have a bad driving record?
Also, giving the car back after buying it does not mean that you no longer owe the money. The car will be sold at auction for whatever they can get, and you are still responsible for the difference plus any interest and fees.