In the burned-out laboratory, it is stated that the liquid nitrogen would have been an accelerant (something that promotes fire). Not only is nitrogen not flammable, but as an inert gas it is frequently used to extinguish fires without additional damage.
The characters pronounce the name "Khione" as "KEE-ohn." As a Greek word, the correct pronunciation is "kee-OH-nee."
After Barry + chair were pushed off the cliff, and Iris jumped even a second or more later, Iris would have gone done always having lesser speed than that of Barry + chair, solely on account of that time lag at the start. Thus, Iris could not have reached Barry mid-air and would have fallen on the ground only Barry has fallen. Weight of Barry + chair and Iris is immaterial because gravitational pull is same on all bodies irrespective of their mass/ weight.
After realizing Cecile's stories were about Iris, Nora states that Barry wasn't in yearbook. However, it was mentioned in "Cause and Effect" that, among other clubs, Barry was involved with yearbook in high school.
However, given that Cecile's story happened when Barry was 11, this would've put him and Iris in fifth or sixth grade at that time. Thus, it's possible that Iris did work on their school's yearbook then, while Barry didn't take part until high school.