Suppressive fire reads: "One strain: Exhaust this card after resolving an attack using "Havoc Shot." Each figure that suffered 1 or more damage chooses to either suffer 1 damage or become Stunned. If that figure was already Stunned it must choose to suffer 1 damage."

Does this effect hit the target of the attack?

The wording of Suppressive fire is a bit ambigious. Looking at the prerelease article introducing Fenn Signes it seems to suggest that only those who take damage from Blast are also afflicted by Suppressive Fire. What's your takes on it?

Each figure that suffered 1 or more damage.

That would include the original target, not just the ones taking blast damage.

The wording of Suppressive Fire is actually quite specific.

"After resolving an attack using Havoc Shot": Havoc Shot adds 'Blast 1' to the attack, nothing more.

"Each figure that suffered 1 or more damage": The initial target has to take at least 1 damage to have 'Blast 1' do any damage to anyone else.

Therefore the initial target is subject to the effects of Suppressive Fire. If they did not want to have the initial target be affected then they would have had to say "Each figure that suffered 1 or more damage from Blast"

I agree with (both) your reasoning, but I wonder if that is the intent of the design or whether something slipped either in the wording of the card or the preview article. It's not unusual that the intention of a game design is not clearly enough worded, or as intended, even with FFG products despite their thorough playtesting. The same goes with the preview articles, for whichever reason, so that articles sometimes misrepresent the rules (has happened a couple of times with X-Wing).

The preview article for SW:IA and Fenn Signis reads that " You can trigger Suppressive Fire whenever you attack using Havoc Shot. Every figure that suffered damage from Havoc Shot must either take an additional damage or become Stunned ." This sentence is not necessarily wrong even if the intent was for Suppressive Fire to also affect the main target of the attack, but it's very misleading if that is the case.

I'm actually playing Fenn Signis in a current campaign and just want to be absolutely sure that I don't make Supprissive Fire overly powerful once I get my hands on this nifty upgrade

But it says "after resolving an ATTACK using havoc shot". Not after resolving HAVOC SHOT. The initial attack hits the target, then havoc shot triggers, then suppressive fire triggers against any units that suffered damage. The wording includes the targeted figure.