You have two instruments in hand, and the two have nothing to do with each other. In one hand, you have a contract for sale. The dealer offered to sell, and you offered to buy, and both affixed their signature. In the other hand, you have a loan agreement. You applied for credit, and the lending institution approved you for credit. They wrote a check to the dealer, and you agreed to pay them back.
In short, your entire beef is with the dealer for breach of contract. The lending institution did all they said they would. At the very least, the dealer should pay their pro-rata share of your note, for the number of days you are without the vehicle, after the date it was promised. I would accept nothing less than cash in hand upon delivery of the vehicle to you. They will probably try to settle on some bullshit deal offering free oil changes, car washes, etc. I would not accept anything short of cash. After-all, it is cash you are going to have to pay the finance company.