1. What are the small boxes in the upper left hand corner of the Strength and Toughness sections of the character sheet for?
A. Those numbers represent the Space Marine's Unnatural Strength and Unnatural Toughness scores. The Unnatural Strength score is further modified by the bonus for the Space Marine's Power Armour. Thus, those numbers include all the modifiers already added in for you.
2. Is there a modifier to hit a Horde?
A. For the purposes of Final Sanction, consider all Hordes to be Enormous, meaning that the Space Marines gain a +20 to hit them.
3. What are the guidelines for cover in the city of Lordsholm?
A. Cover doesn't impact your chances to hit, it adds Armour to that location. Consider any cover in this adventure to add 8 APs to any appropriate location protected by the cover.