Hi there

1. You do have to charge in a straight line. However, if there are obstructions in the way ( columns, buiding's corners, other models), you can move around them.
2. You roll an advance. If you two stats can be raised, roll which stat is raised. If that stat is maxed, you MUST apply it to the other stat ( that would be Wound stat in your example). If both stats are maxed, you can apply +1 to any stat, but note that you can't exceed racial maximum.
If only one stat can be raised and is already maxed (this is possible only when you're rolling Henchmen advaces - note that Henchmen' stats can be only raised by 1), roll again.
3. Regeneration comes into play when a wound is inflicted. So you regenerate the wound before it's doubled.
4. FAQ:
Q: Models with missile weapons that are up on a building or wall - can they trace a
line of site to a model standing against the building or wall (assuming that the model
with the missile weapon can lean over the edge and look down)?
A: Yes.