Those seats are nice. 2nd level behind homeplate and you have dedicated servers/waitresses that bring you drinks and food. Most/all of those seats are owned by businesses, and are given to employees/clients for free. Guy selling them on kijiji (if they are legit) probably got them for free and is looking to make a quick buck. I'm not sure its worth the risk for 100 bucks, though you might be able to talk them down to like 50$
I'd probably take the hotel nearest to the park. There are lots or restaurants and bars nearby
Also note that the airport is not really close to the downtown core, its probably a 30-60 minute trip depending on traffic. (EDIT: forgot about the new express train, that should make it a quick trip.)