With your other choice being a Tiffin, I don't think you would have fared any better. If you read the Tiffin RV Network Forum you will see people spending weeks and even months at Red Bay, AL, waiting for repairs for things that sound like they should have been caught at the factory.
Yes, it does sound like you got a lemon, but it also sounds like the issues should be fixable. It is frustrating when things go wrong with any large purchase, but hang in there and give Newmar an opportunity to correct the problems. I don't think demanding or even suggesting they give you a new motor home would be a method to get things fixed.
2011 Berkshire 390bh