I'm not sure if you're looking for feedback on the setting, or on the .pdf as a player resource, or both. My comments are a little all over the place.
1. I love that picture of Smaug. It's also a great reminder that treasure needs to save against breath weapons.
2. For me a 'sandbox' setting doesn't include a lot of player-metagenerated content. Players change the setting through their characters by exploration and interaction with the setting during actual play, not by creating it whole-cloth out-of-game.
3. I really dislike checklists of questions in any case.
4. Is it really necessary to force the adventurers to be prisoners at the start? Why can't they be just fortune- and glory-seekers who share a common starting point?
5. I don't see anything by way of advice to players intended to facilitate their participation in a game with no adventure path to follow. Thirty years ago no one needed an explanation on how this works; now it seems to be something of a lost art.