Sorry to hear what they are doing to you. It brings back the nightmare of my old 07, dealer pulled the engine 2 or 3 times, replaced tranny, etc I bet they spent $25k in warranty work trying to fix the truck before giving up and declaring it was fine and refusing to do more, forcing me to sue them, or sell the truck. I opted to sell the truck, but I regret not suing them and hold them accountable. The previous owner sold it because it was a lemon, so did I and the person I sold it to took it back to the same dealer later for exact same problem.
Because they know upfront how big your bill is, they are going to dig their heels in, if it was maybe a 2-3k repair they would likely cover it and maybe even get up to 20-25k before giving up, but knowing ahead of time the cost, they'd rather gamble on getting sued. They think about it like this, if they deny $1,000,000 in warranty claims, they might get sued for $50,000 of them and pay even $50,000 in legal fees. That's still $900,000 in savings. Sad but it's how many big companies operate. It's also why when they make the truck, they are happy to save $1 on a part and gamble on how long it will last because even $1 translates to massive savings overall even if they replace some.
There's a few important factors, first the original bill of sale will state the warranty, unless they prove you did something to void it, it's still valid. I had to sue the dealer on one truck I purchased because they claimed it was a used truck and the warranty started 2 years before I bought it even though bill of sale stated brand new full warranty and refused to change and the manager told me if I had a problem to sue them, so I did, as soon as they got my lawsuit in the mail the general manager of the dealership called me and kissed my ass in order to resolve it.
BBB is absolutely useless and FCA will laugh it off, they have no actual power. If you have any hope of getting this covered you need to show them you aren't backing down or going away. I'm in Canada so I can't speak to all the laws there, but if you can, I would prepare and file a lawsuit yourself, just pay a lawyer a bit to help with wording and look over it that way it will only cost you a fraction. You won't be suing just for the repair, you will be suing either for the interest on the loan, or what it cost you to use another truck for the time it's down. It will show FCA you are serious. I would also contact the dealer you bought the truck from and hound them about doing something. Where is the truck currently? If it's at a dealer I would get it moved, you don't want them having access to it anymore unless you have commitment it's going to be fixed.
You also need to make a decision, either sell the truck as is, fix it, or leave it sit until everything is settled (I don't recommend this option). Fixing the truck IMO is the best solution for having proof of what caused the failure to help the lawsuit, you can have the shop who fixed it provide sworn statements about what happened. FCA without opening the engine doesn't know exactly what happened. While the computer tells a lot, it will not tell the exact story and gives you a massive benefit. If you get it repaired, pick the shop very wisely. It is very important to pick a shop who conducts themselves very professionally and who will help you the most in the event it goes to court. Some mechanics are great mechanics, but making statements that lawyers will try to pick apart? Not so much.
