From your post, you got scammed and you allowed yourself to get scammed. When you buy a vehicle, you get the title. At the very least you should review the title, but it would make no sense to do that without actually getting it. Sure, you can spend time and money pursuing them, or even reporting them to the police. That may or may not get a dollar of your money back. It might be an expensive lesson learned, but it might save you a lot in future transactions. You mention Bankruptcy, but don't tell us how that is relevant.
Have you put any of these requests for title in writing? You may want to do so and explain that you must have the title to have your tag issued. You may have told them this a thousand times, but this letter needs to be sent certified, return request. Then, if you must take them to court, you have evidence that they were informed. It sounds like these people who took you in and raised you got into some financial difficulties. You may be on poor terms with them now, but you may not want to burn any bridges, because you may want to continue a relationship down the road.
You may want to see if the town you are in has a legal aid office, or if the local Bar Association has a pro bono (free) legal assistance program. You do not want to get in trouble with the local authorities about the tag, but as long as you're in school, you may be able to continue using your adoptive parents' address. Talk to a local attorney and see if they have any suggestions.
This is not intended to be legal advice or create an attorney-client relationship. If more information is needed, you should consult with an attorney in your state regarding the specifics of your situation and the options available to you.