1) What is the maximum hero lvl you can reach?
Depends on the chapter.
2) What are the maximum skill level values for regular and the ultimate skills (meaning the ones you choose in the settings; ultimate meaning the last ones you get to pick (like phoenix strike, northern winds etc).?
Since we can't reach the level cap yet, we don't really know.
3) What is the maximum level for the combat kings?
5.
4) Where do you find / How do you trigger battle with --- the Ghost Wolf in chapter 5?
Kill a certain amount of wolves.