Regarding the payoff: Why is the player collecting the various facts about the monster? This game ends with a mad dash for the exit in a maze, which doesn't have much connection to the factoids seen earlier in the game.
Game mechanics usually build on each other, culminating in an ultimate point. It's a bit like school, where you have homework and quizzes throughout the term, and a final exam at the end. In some games, this is a boss fight; in others, it's a massive puzzle.
One way to build toward a payoff would be to make the maze relate to the facts the player finds, so when the player has to run for the exit, the player can use knowledge from the clues to identify key landmarks that designate the correct path. Another way would be to scrap the factoids altogether and make the game a series of mazes to complete, starting with mazes that are smaller and not timed and gradually advancing to larger ones with time limits. Bear in mind those are just two ways to do it; look to other games and experiment and you may discover other ideas!
As for the music, I have been making custom audio for my projects and have set up Audacity to export .ogg and .m4a versions of my audio files. Click one of the links for the operating system you are using to see how you (or your composer) can do it too:
Once you have it set up, it's just a matter of opening the audio files in Audacity, going to File > Export > Audio, and choosing .m4a.
I hope that helps you with any future work you plan on putting into this project and future projects!