3.) Are the events of this story what led to the more aggressive/violent disposition of the Borg encountered in "Greater than the Sum", and later TNG novels?
Haven't read it yet, but I don't think so. Resistance
introduced the more aggressive Borg behavior and explained it as a defense reaction of an isolated Borg population that was in the process of growing a new Queen. Since the Queen was vulnerable, the drones had to be extra-aggressive to ward off any threat. The Borg seen subsequently in Before Dishonor
and Greater Than the Sum
were offshoots of that same isolated population, so they continued the same behavior pattern. It's unlikely there could've been influence from any other source.
The aggressive tactics of the Borg in Destiny
had a different origin. This was the core Collective back home in the Delta Quadrant, which had been isolated from other Borg populations since "Endgame." They had decided that the Federation was too great a threat to their safety to tolerate and thus mounted a campaign to eradicate it once and for all. Again, it's unlikely anything going on in the Alpha Quadrant subsequent to "Endgame" could've had any influence on their behavior, since there was no known mechanism for contact.