Given that I'd allow someone to do what you've listed, for no cost at all, I find this particular power a bit underwhelming. (Consider, for reference, the text on page 230, where it suggests that one can treat any form of magical barrier, from running water to a Circle, as a threshold. Consider also that this seems to be the *only* reference I can find to protective Circles in the rules. And consider that we know a relatively ordinary person can - if they know what they're doing - set up an effective defensive circle fairly quickly.)
Also compare this power to taking Rituals with a focus in wards; ignoring for the moment that warding rituals allow much greater flexibility in effect and also grant enchanted item slots, a character with rituals and, say, lore of +4, could make a protective circle of double the strength in a third the time or less - and they could tag aspects or accept consequences to dramatically increase the effect.
I'd suggest an alternative version:
[-1] Ward of Faith: The True Believer may spend a fate point to bolster an existing metaphysical barrier with her Faith; in essence, converting all magical powers (including physical attacks from supernatural creatures) that attempt to cross the barrier (in either direction) into mental attacks against the True Believer (who may defend with their choice of Conviction, Discipline, or the base strength of the original barrier). The True Believer must focus to maintain this protection; supplemental actions and regular defenses are possible, but any attack or maneuver results in the Ward of Faith automatically failing.
A typical taken out result in such a conflict would be the Believer lapsing into unconsciousness, the barrier collapsing, and whatever action resulted in the taken out result proceeding unimpeded; a typical concession results in the destruction of the barrier (though this may not be appropriate if the True Believer is bolstering a powerful existing ward), and whatever action prompted the concession proceeding at reduced effectiveness as per the normal block rules.
This could be used in combat with a maneuver (probably based off of lore) to set up a pre-made "portable Circle" - which would on its own function as a strength zero threshold; this would probably protect a small, tight group of people at most; anything larger than that, and you'd need multiple exchanges (or, preferably, out-of-combat preparation time) to get an appropriate taggable aspect in place.
