FE5 is rally red.
One of the better colors produced by mopar.
9/21 is the SPD scheduled production date
The door tag is the actual end of production date
Nothing out of line there.
Can you post pictures of the door tag and if possible when you have the battery out a picture of the other half of the inspection tag that is connected the trim tag. There should be an inspectors stamp on it. I wouldn't bend it.
Also, if you found the original front seats was there a build sheet in it?
There should be a broadcast sheet under some of your seats. It seems that often times the C's have a broadcast sheet in both the front seat and the rear seat.
There could be a BS behind the glove box or under the carpet. Have seen one in a headliner before also. Keep any scrap you find of the broadcast sheet.