Thank you for your review! Dont worry - night mode supposed to be extra difficult, even I completed it only once in ~50 tries. Each mode is approximately 2 minutes long, if player dies - new wave won't spawn, so ye, there are tons of chairs supposed to be after.
Actually being on fire is not for a cosmetic purpose, you can notice a round progress bar indicating total time you can stand on burning floor, if it fills - player dies. At some point you will be forced to step on it to dodge chairs, but be cautious to step off after!