Folks who regularly deal in auto fraud, like my firm, will likely give you a free document review. Based on what you have stated:
1- Dealer financed you, so, dealer is likely a buy here pay here dealer and as of Jan 1 needs to give you a warranty. Failure to do so could really hurt dealer here.
2- After the repo they can only ask you to pay in full IF certain things happened prior, like multiple repos or you hiding the car from them. Otherwise, they can be in trouble for doing this too.
You should look for a firm who specializes in this area of law to get help right away.