The rules for the tax credit state that you must be the first person to put the car in service. Which means if the in-service date and the purchase date are different you are out of luck. https://www.irs.gov/pub/irs-pdf/f8936.pdf page 3
Keep in mind, that the credit is offset against the taxes you owe, if your total federal tax liability is less than $7500 you will not get the full amount. Check line 63 on your 1040.
I have a "fleet discount" through my work, which looks similar to the CCA discount (can't combine the two). It states that the demo cars are not eligible regardless of the mileage, the rule must be the same for CCA.
There is a way to enter the service menu, which will show the battery capacity, but I don't know the steps.
Please share the price you got. I'm also interested in 2014.