W.P.
Dear J.:
Until you are divorced, you are still married. That means you share things, so you can use his car. To take it away, he'd have to come and get it (which he could, but he'd have to actually come and get it). I don't think he could repossess it or sue you over it. Follow through with everything else, or you'll regret it later (unless you want to reconcile).
The court will decide who gets what, so if you don't get the car, you will likely get a few other things and definitely some child support. Then you can buy your own.
Either way, you don't want to depend on your ex, and you should want to legally be divorced to start a new life.
Regards,
W.