The grenade idea was incredible. Really top notch work with it. I'm surprised that it worked on the Hogwarts grounds, but it works well with the story.
Hermione's question is an interesting one. I think it's pretty obvious that Remus died. He was stabbed twice, with the silver knife left inside his chest right next to an exploding grenade. Harry's statement probably didn't apply to him, though. If I had to guess, I'd say Ron is dead, either him or someone else caught by the blast.
The other thing in this chapter that I found quite uniquely impressive was the Ravenclaw Sisterhood's allegience. Well done.
Looking forward to more.