There's no way in hell they'll just take the car back. These are things that you are supposed to look for before buying the car, and part of the purchase agreement states that you are aware of the condition of the car and that you cannot return it because you are unsatisfied with it. It was INCREDIBLY foolish of you to not properly examine the car before buying it, and quite honestly, I'm laughing at you too. Your only hope is to try to get a friend to try to fix some of it up for cheap and to try to sell it for, well, even fixed up you can only hope for a FRACTION of what you paid. I mean you really screwed yourself over here. I'm not trying to be a jerk, I'm just being honest.
So basically, you can't return the car, he doesn't have to take it back, he doesn't have to give you your money back, you can't get your money back, he is not obligated to fix it in any way, shape, or form, and he is not obligated to find you another car of equal value.
He has every right to laugh at you, and there really is nothing you can do. You dug your grave, now you must lay in it.
