Okay, let's go straight to 2 here; I had stated in the introductory post that there was grass 'as far as the eye could see', which implied that the group was deep enough into the center of the plain that leaves of such a size would probably not make it there (you know, because physics).
As for 3... 'sea of' would imply the grass to be of relatively decent height, and even then it's basically a tinderbox even if you do try to contain it. One slight breeze and one little flame moving a bit too far and BOOM, whole place is ablaze.