Okay, so I completed the book.
Yes, they did mention that Stilson died. I think the reason it wasn’t addressed in the movie is that the point was essentially made by Bonzo dying, and since Ender wasn’t told anyway, it wasn’t crucial to the story.
Second, in the book they didn’t just pop up and make the planet go boom. There was, in fact, a similar effort of using the fighters as shields and making the tunnel formation, just like that battle in the Battle Room against the three armies. He in fact did use his superior tactical skills to accomplish the objective - taking time to maneuver closer to the planet while appearing random, using the formation tactic to create an opening through a large swath of the defending force, before finally engaging the planet with the Dr. Death.
As pointed out, though, they did gloss over the reason Ender went with that strategy was he felt the adults were cheating with their simulation by giving him an impossible task - a tiny, antiquated assault fleet against a bazillion enemy ships. Thus he felt justified in cheating himself, going for the planet itself, and hopefully they would then disqualify him and he wouldn’t have to continue. He was physically, mentally, and psychologically exhausted.
Before the battle begins and Ender mentions attacking the planet, Mazer reacts pretty hesitantly, suggesting Ender should really consider if he wants to escalating the attack against civilian populations. But when all the adults see the situation and the number of defenders, it looks pretty hopeless, and they realize that Ender’s solution is the only one.
The other thing that stood out was I do not recall reading any of the material after that. I don’t recall reading about the wrap up on the Earth revolt, or Ender going on the colony mission, or any of that. In fact, that was what I came out of the movie wondering about, because I don’t remember it from when I read it before.
I see why they put the stuff about the queen pupa on the asteroid for the movie instead of drawing out the story with the colony ship and discovering the planet. They successfully captured the essence of that, finding the reason the asteroid ruins looked like the castle ruins in the game, and the interior looking the same, leading to the prize. It was a bit weird having the living queen there. I guess that was an element of trying to make sense of how the queen could be communicating with Ender via his dreams to pass along information and yet he only finds an “egg”. Instead of the queen in the pupa being the one contacting him in his thoughts, it’s the old queen who is ready to die. Maybe they felt that would make more sense for the movie audience.