1. See above.
2. They are only skill hits if he does them with full morale. Is this the case? From what you are describing your first hit sounds like skillattack, the second as a physical attack.
3. Flavius is a great hero to use against adamanti. Also getting skilldefense up can help. And, see above.
4. See above (Maria heals for the amount of her magic attack)
5. Opinion only; leave smoulder, dawnbringer, horemheb and Mulan. For most other heroes I have found uses. It depends on where you are in the game whether or not you need them.