This is really unacceptable!

You started having issues with the car on March 24th, 18 days later you still don't have your
brand new car. And you've been stuck with a car that's not even in the same size class as the car you're supposed to have.
A few points:
1) Your dealership has been totally unreceptive to allowing the possibility that there's something with a newly designed car.
2) They were trying to place blame on you.. "you put bad gas in" "you misused the car" "you don't know how the smart key system works"
3) They get around to diagnosing the car
A WEEK later after you bring it in and finally discovered that it's not YOUR FAULT.
4) They haven't made this a priority
Make sure these things are always fresh in mind the next time one of their customer "service" reps try to shift the blame/change the issue/delay. I say, if you don't have your new car in the next few days. it's

PEOPLE's Court Time.
No seriously, it sounds like they've been negligent in fulfilling their duties as a dealer. Who knows how many other customers are getting this kind of treatment because no one's taken them on.