2. Each person will have different level due to units they may have. It it simply a matter of doing as much as you can before you are forced to level your way up to the next cap. 10 > 20 > 30 > 40. Of course as has been mentioned around Castle Retake is when you will normally be forced to CC units.

3. I personally have not used fairies to level any of my units outside of what I mentioned. Haven't gotten everything I have to 50CC50/50 yet..

9. Yeah it is for later after you have your core. Granted I'd probably have around 2000%+ if I didn't raise girls affection simply to do that.. Guess it is a benefit of being here from day one.

10. It is for the benefit of your own level and your units level as well as gold to level said units. Doing something like Return to Ruins will eat up your gold like nothing else despite level units faster.

12. All the male only maps can be beaten with extremely low level iron units from what I remember doing. They aren't at all hard. Only think I needed chrristopher for Mens Battle 3. Even then I never leveled anything.