Manuals for playing Inferno

Could you please provide the formula for calculating Hellfire? Does the damage depend on the number of creatures in the unit, or is it calculated using the formula 10*(spell power+1)? In other words, if a hero has a spell power of 10, will the enemy creature receive an additional 110 fire damage?
Does Hellfire affect the Soldier's Luck skill?

Hellfire
Creatures under the command of a demon lord have a 30% chance to deal additional fire damage during an attack. The amount of damage is equal to 10 + 10 for each level of the hero's "Spell Power" skill. When this ability triggers, the hero spends 5 mana points.

It should affect it.

You can find the answer to this and other questions in the manual compiled by the Age of Heroes website.