Certainly an eye opener...
A couple of those issues should have been picked up in the PDI but I can understand your frustration. For me I would be most concerned about the loss of 5 gallons of hydraulic fluid and where that residue now resides...I'm sure it's soaked into some things that will be out-gassing those fumes for a long time.
About the cabinet hinges, one day I just bit the bullet and went through EVERY hinge inside and out and re-did just about EVERY screw hole with wood putty or epoxy. I couldn't believe the amount of screw holes that I had to strengthen.
You must have the same $1 a square yard carpeting I have, purchased a throw rug for the dining area and I'm in the process of getting some carpet step protectors to keep the wear down.
Some of those problems are dealer related, not that should really matter they are Keystone representatives.
When I bought my Cougar I knew going in that this wasn't a top quality camper, I could see that on the few Cougar 5th wheels we looked at prior to purchase, BUT we got what we paid for, a decent unit for $20k something that if after a few years the wife and I weren't happy with we wouldn't go bankrupt selling it. As it turned out we love camping and have upgraded the suspension, tires, heating, batteries, etc and now 4 years later are very happy campers (pardon the pun).
I wish you well and hope Keystone does the right thing.
Ron W.