IMHO, because Krys' word is what counts:
You only need See Invisible (Spirits) if you want to be able to perceive them without employing Medium. Sounds to me like a clear candidate for a power to drop, unless you can think of a scenario where you'd need it.
"Very Blessed" is pretty clear that "the reaction bonus from your god's followers is +2" -- but may run afoul of Krys' desire to avoid things Divine. If it gets nixed, perhaps you want to consider a Reputation +2 (Great "medicine man"; Large class, spirits; All the time) , though that doesn't get you the bonus to interpret visions.
GURPS Powers offers a +0% "Active" enhancements to Terror that converts it into a single-target ability. You take a Concentrate maneuver to affect the target (within 10 yards, and able to see or hear you, depending on which sense you specified at purchase) and roll a Quick Contest of Will (with the target at a penalty based on the number of levels you bought). If you win, roll 3d for his Fright Check, but add your margin of victory instead of his margin of failure.
Note that Powers also offers "Awe" and "Confusion" variants of Terror, in case that suits your concept better.
I agree that Selective (+20%) would probably allow you to exempt friends from Terror. I seem to recall that somewhere that sort of thing is specifically cited (as for a dragon), but can't find the reference at present.
Do massive levels of Charisma really fit Howahkan as described? I'm wondering if a Reputation with spirits, rather than an ability that affects everyone, might not fit the concept better.
EDIT: Characters p. 37 states, "As with Dependents (p. 131), the GM will adjust your Ally's abilities in order to keep his point total a fixed percentage of your own as you earn points. This will keep his value as an advantage constant. The GM decides how the Ally evolves, though he might ask you for your input."