You didn't "blow it" by setting firm boundaries. The car is in your name, of course he's not taking it. Take the keys away from him if you have to. He's working, let him buy his own car.
If you have any joint financial accounts, take half the money out and put it in your own private accounts.
You need to step back a bit and take off your rose-colored glasses. I know you love him and he's the father of your children, but he's abusive, disrespectful and probably a narcissist. You've been putting up with way too much for way too long. You may not even be able to see how abnormal this relationship is until you have some space from it, or are in a new relationship with someone who treats you with respect. I know that was true for me.
Good for you, btw, for starting your own successful business. Keep the focus on that and on providing stability and joy for your children. Nurture your friendships and family relationships.
And even though you're not married, consult a lawyer to find out your rights!!!!
