Unfortunately, the definition of "new" doesn't always mean "brand new and never touched"...at least for vehicles. They have often been test driven...perhaps by a number of folks. I once bought a Wrangler literally off a showroom floor. Who knows how many people pawed it first. They are probably not required to notify you that it may have been shown at an auto show...just as they probably don't have to tell you how many people climbed through it at the dealership. Granted, when it is at an auto show, there are probably a heck of a lot more people climbing through it.
The good news is that they seem willing to work with you. They could have said that it was fine on delivery and that you did that damage. If I was you, I wouldn't burn through their "good will" (yeah, I am using quotes there). Instead, I would work with them to fix all of the issues...including the dent in the hood. Frankly, that is what would torque me the most here. I would accept the new window and the fix on the sliders...unless you can point to other specific issues with the roof. I'm not sure what you mean by "left side of the passenger seat is weak". Can you elaborate? Replacing an entire seat seems like a fairly significant expense, so I would expect some push back there unless you can point to a significant issue that is obvious to them as well.