I'm sorry but I would not be so quick to condemn the dealer at this point.
You have to admit first off that such a problem with a brand new engine with less than 500 miles is unusual, to the point of being almost unheard of.
When troubleshooting what appears to be a simple miss on the surface, the LAST thing you do is tear down the engine. You look for external causes first. They pulled the plug, it was fuel fouled. They looked at the gas. It looked, by the OP's own account, terrible. Not a huge leap to go from bad gas to fouled plug.
That didn't fix it. Okay, new engine, so still going to exhaust every possibility before tearing it down.
To me it sounds like they did the logical thing and kept troubleshooting the simplest/easiest things left, first, until they found the problem. Sure it took them more than 10 minutes, but it was a highly unusual problem! Who's going to go straight to "bent valve" on a brand new engine? Nobody!
Really the only thing in question is what will be done to fix the issue. That's up to Chrysler. They have policies on how to handle situations like this, and you will have to play the game. Demanding a new engine, is probably not going to yield a new engine. Showing them this thread isn't going to help either, as this forum is not recognized as an authoritative resource by anyone. The only opinions that they will take into consideration on mechanical issues, are their own.
The best shot of getting a new engine sounds like it would be working the "piston" angle with the dealer's service writer. You know, that piston looks a little banged up, and that cylinder appears to be scored...