Oh my. You have maybe four or more questions in that giant paragraph. Hard to figure out where to start.
Assume as a 2014 model you are out of basic warranty. You only hint at that with your introduction of some kind of extended warranty. If so, that means you may still be in the Federal Emissions warranty period. But is that part of the issue?
You paid probably lots of money and time getting a variety of things done but still have no conclusions as to what is wrong. Until that is done I would not venture any more guesses on future recourse. Find out the problem. Then make a decision on what to do.