1) Don't use bolts. Axes ftw.
2) You can't, be careful when deploying them. Stage them somewhere first, make sure they're all there and no one's lagging behind, then move them to the battle. Having a staging area is important, and can be made simple if you make a burrow behind a drawbridge for them to guard. They go in the burrow, then you can lower the bridge and they spill out all at once.
2b) Sight range seems to depends on tree coverage and terrain. Ever played adventure mode and noticed the way you can't see in cones behind trees?
3) Animals on chains (not necessarily pet animals) or keep your people inside. Goblins path towards your fort, and if no one is outside then they path directly. You should only be outside for wood anyways, right? Animals can help lead them along a path, and war bears tied up every 10-20 squares will ensure that they go from one to another, and get mauled along the way.
Also, as for deploying, I've toyed with this idea with good results. Have your military inside a square of bridges. That is, drawbridges that, when raised, create a tight room. Surround this room with no-ramp channels to ensure security. Have this room accessed via underground tunnel and lockable hatch (via switch, not forbidding). Make a burrow inside the room, or even make this their training barracks. When enemies arrive, your soldiers can move to the bridge-room, then you lower the bridges to turn that whole area into one section of flat terrain, allowing your soldiers to rush out easily. This can be effective if you put the room outside your gate, so that you can lock the gate and still deploy your military outside safely. If this is their main barracks and there's no roof, then it will also prevent cave adaption.