Audio support in C2 is dependent on the HTML5 audio support.
And that support is pretty restricted atm. It only allows playback, and options like speed of playback does not work in all browsers the same way.
Audio support has been widely treated in Scirra's blog (be sure to check in the archives)
XBOX live export is not likely to happen either.
The focus of C2 is and always has been HTML5. More than the fee you're mentioning, there is also a question of converting the exported projects to C# or a like-language that will then be compiled through other tools to be used on Xbox.
Scirra has also been talking about this in the past explaining that their resources (a two men British startup) could not be able to handle such export and if they did, they wouldn't be able to keep on focusing on HTML5 and bringing all the new features they do in their quick release cycle.
And for competitions, there weren't some in a while, generally they are announced in the stickies or announcements of the forums, post on top of the index list in "Construct 2 general" (or even through all the forums). They also are announced on Scirra's twitter (@Scirra) and facebook (link).