To use Threat as your MC’s Unique Ability, I think your story will need to put its dilemma question in the area of whether or not the MC is sufficiently aware of the dangers coming from his web-posting actions, and if the “good” he has calculated will result form his postings can still be accomplished despite the dangerous jeopardy he is putting himself and his loved ones in.
That is, if the MC believes his mentor is wrong, and that “the authorities” won’t quickly enough take the needed actions to capture the murderer/executioner, then his Unique Ability of discerning and gauging threat could turn out to be the problem-solver.
Basically, I’m suggesting the MC calculates that his photographic web postings could make the executioner get nervous/careless — and perhaps even get him looking in the wrong place for retribution, because website addresses are a lot easier to fake than property addresses.
And (so long as yours is a Success-Good story), your Steadfast MC turns out to be right despite all the contrasting “wisdom” and close calls.
If so, I see such a story aligning well with other Dramatica Story Examples that have a Steadfast MC with the Unique Ability of Threat — like The Incredibles and Mr. Roberts. Both of these, I believe, come down to the MC properly gauging the power of the threat against the promise of the gamble.
Of course other Dramatica Story Examples with this same MC Unique Ability end in Steadfast-Failure-Bad (the MC of Double Indemnity did not properly use his Unique Ability)… or Change-Success-Good (the MC of Some Like It Hot did not properly use his Unique Ability of Threat until after he had Changed).
Does any of that help?