2.) Yes, definitely. And they will. ALL THE TIME.
7.) Probably won't alert them to your location THAT way. But just the fact that their ship blew up alerts them to your presence, so prepare to be actively sonar pinged, and they'll tend to find you pretty damned fast.
8.) Generally, for most merchant shipping, it's the engine room directly below the smokestack. Some merchant ships have BETTER places to hit, but if you aren't aware of what those are, aiming for the smokestack is a pretty good bet.
Those are the only ones I know the answer too, hope I helped.
