Can't say I've had any sound problems. There's a readme attached to the demo that discusses potential problems with video cards and sound cards, so you might want to look there if you haven't already.
Other than that, I'm not sure how to fix it.
NoRemorse - as far as enemy fighters being unable to shake you goes - don't worry, it'll get harder. Part of it is that your guns can traverse throughout your forward arc, so it makes it easier for you to keep a target aligned. But your enemies do have ways of getting back at you. They quickly start mounting turrets that can fire at you no matter which angle you approach from. Also, after a while, the numbers start to tell. I actually managed to get destroyed at one point. I'd gone to check one of the locations on the map while looking around, and ended up in the middle of a brawl between local law enforcement and pirates. Before it was over, my hull was at about half strength. Then on the way back, I had an encounter with a group of pirates camped out on the lane, and they managed to finish the job that the earlier group had started. You may be on the tail of one of their fighters, but that doesn't mean there aren't three or four other guys sitting on your tail.
Unfortunately, I never thought to use my nanobots for repairs, or things might have gone somewhat differently.
Which reminds me of one thing I found annoying. Presumeably, the pirates shut down one of the accelerators (or whatever they're called) on the lane, and that causes you to slow down so the pirates can attack you. The only problem with that idea is this - immediately after I was pulled back into normal space, a group of ships went whipping past using the lane rings. I would have thought that they'd be forced to slow down, as well.