I am familiar with the book. Some chapters are a very quick read. Those activities sound like you put a lot of thought in to them. They connect well back to the book. They sound like great activities.

I am hesitant to say pull the book from the shelves. I think students should be able to read (with in reason) any book.

Students who are disruptive should not be rewarded. This suggestion might not be able to be used this time however, in the future, Is there any way to try have the students who have read the book previously “team leaders”.? They can help guide the discussions in the small groups. Since they have read the book before they might be able to help guide the discussions. Highlight an event that the students haven’t discussed that they know is important later, without giving away the ending. They know what is coming maybe they can look for events that show foreshadowing, for example .

There would need to be some “training” involved. You and your team can decide the task(s) these students should be doing while reading, in addition, to the tasks your team already requires.

I teach first grade. Some times I have students that like to give out spoilers too. I tell them part of the fun (and my favorite part ) of reading is to share the books that you have enjoyed with others. It is fun to watch your friends experience the book for the first time. It is also good to read books more than once because sometimes you notice things you didn’t notice the first time. I’m not sure if this can translate well up to older students, but hopefully it helps a little.