Windnut,
A standard-sized dinette booth doesn't make a full-length bed... ours is also 5' 4" long. If the booth seats were any further apart, the tabletop (when lowered) would be too narrow to reach the booth seats/frame to complete the center piece for the bed. From your description, I'm guessing that your booth is probably installed correctly.
It does sound like a potential "oooops!" by the dealer though, if there are mis-matched colors & incorrect cushions.
As for the gap between your booth & sofa -- although we have a Laredo, we have the same booth/sofa 'furniture arrangement' in the slide-out... there's about 3 inches of space at each end of our sofa - the sofa is centered in it's designated spot.
Here's some photos of your model showing the standard booth & cushion size.
http://www.summitrv.com/rv/keystone/...e_Cougar_27RLS
http://www.campingworldofchattanooga...-cougar/109933
Hope this helps,
Terri, the Chevy co-pilot