I would like to be more sympathetic but come on man! You didn’t check your gas gauge, went riding out in the snow and then lost your gas cap! I will agree if you had it in writing that the tank was to be full they do owe you that. Sounds like you want to blame everyone else for your failure of paying attention to important details.
As far as accessories, new popular machines like the Viking may require a wait for some of the add-ons. I have been on hold since October for one of mine from Yamaha. The dealer can’t control that. I do not work for a dealership.
Are you happy with the performance of the machine? You have used terms like terrible and nightmare but from what you describe in your letter it sounds like the only thing the dealership forgot was filling your tank. If you want to read some horror stories about bad dealers just check out what some of the Polaris owners have to say.