The first set of number listed before each date is the dealer ID number, not a mileage number. It simply means the car was passed around to a few dealers pretty quickly. That's not real unusual. Many large dealerships won't keep a car around that is past a certain age or mileage. Many will sell it to a smaller dealer, and that smaller dealer could have taken it to an auto auction.

Carfax is as good as the last update.

Seat frame: I ran a small welding shop for 25 years. I've welded up a bunch of car seat frames. Most car seat frames are not designed for the super big people. When the sit in them and wiggle around (ever seen a big person get in or out of a smaller car? Its a wonder some last as long as they do), the seat frames crack and break.
Rusted and patched rocker: Rust happens in the rust belt. Repairs are not always that good. You would be amazed what people will do before they trade in a car, just to get a few more $$$ for their trade in. The dealer may, or may not have know about the rockers, but many wouldn't care on an older car. If it looks good, they get more money out of it.

Sorry to say, but it sounds like you should have checked the car over better before you spent your money on it. Its your's now. What are you going to do with it? Gene