The evolving soundtrack is an amazing idea, heck! Thank you very much for that suggestion and feedback!
It was the first time any of us had to create a soundtrack for a game, so the background music was just a means to fill the silence - but encorporating it like this to show the tension (besides some simple pitch manipulation that we have thrown in) is such a clever idea!
And I totally agree on your other points as well, thank you! :)