1. I always assumed 270 degrees - they can't shoot through the Obelisk, but apart from that if you can draw Line of Sight you're a-okay. I can see an argument for 90 degrees being made though - a lot of people still believe that if it's not specified, it's hull-mounted by default.
2. Pretty sure it'd hit Allies of Convenience.
3. Seems like a pretty reasonable dude to bring along, powerful guns and survivable.