1. Depends on your group/unit, and what roster line you are on (dependant on endorsements). Evens out to 9 x 8 hour days a fortnight..
2. Most groups/units have a leave planner, but this is normally allocated at least a year in advance. Not many issues with being able to take your accumulated leave at the moment.. You just need to get in early! Most groups also use a points system for popular times (xmas, Easter, school hols etc) to try share those around
3. Overtime availability also dependant on your group/unit.. Mine has been surviving on it for years! Some are a little better staffed.