Don't worry about BF%; look at the mirror
Looks like a great starting place.
The calorie counters are not good for discovering your needs, they are good to discover the direction you need to go. What ever calories you were maintaining at is what you should build on. Just add 200 to 400 calories to your current maintanence level and monitor. Adjust according to results. i.e. look in the mirror and check the scale. If you are heavier and not gaining much in the way of blubber, then keep that calorie level, if you are getting soft, then cut back, if you didn't gain, increase. Do this every two weeks.
See above. The length of time is impossible to predict.
Don't worry about it, see above.