How does the scaling *+ of the 0-2 range of effect work? Is it one target within 0-2 that has dangerous and obscured terrain per each opportunity * symbol kept ?

The text explicitly refers to the 'area', so I would assume that is would affect the area within range 0-2, including all living individual entities within said area.

I'd agree.

"Activation: As an Attack action, you may use two doses of any single poison and make a TN 2 Medicine (Air) check targeting each other character at range 0–2."

So the basic activation affects everyone in range and defines a range 2 "bubble".

"Air +: Until the end of the scene, the area at range 0–2 becomes Obscuring and Dangerous terrain."

My personal suspicion is that the '+' here is erroneous and it's not a scaling effect.

Normally, when you see a ' +' option, the effect is 'do XYZ per spent' (just like the third opportunity on Noxious Cloud, as an example!). Making the area Obscuring and Dangerous is something that only makes sense to do once, though, and as @Tenebrae says, it's already worded to apply to the entire area.

That’s the point of this thread and my question: What is the correct implementation of the opportunity number two ( the *+ ) option. One could also interpret that for every * SPENT, after a successful TN was rolled, each target within 0-2 suffers the Obscuring and Dangerous terrain effect as the poison affects each target ( but potentially not ALL targets within 0-2 suffer this secondary effect after the initial damage; only those targets with 0-2 where an opportunity * symbol was spent ... ).

I can't speak for RAI, but I'd agree with @Magnus Grendel that the '+' is in error.

EDIT:

Upon review, I can't help but wonder if the top opportunity entry should have been

+: move 1 range band per spent

... or something to a similar effect.

Waiting for an official FFG ruling on this one. Thank you for the replies!

2 hours ago, Vulcan64 said:

Waiting for an official FFG ruling on this one. Thank you for the replies!

In that case, you may have to make them aware of you need. As well as communicate the intensity of your need for such a ruling.

Using the official contact form has worked quite well in the past. It's not super fast, but does get answers in general.

Done. Thanks!