So here's what I'm thinking. 10d6 is hopefully enough to actually stop the spears? Maybe not...I
[X] Plan Shieldwall And Fire
-[X] Stoke Frami (+43 Orthstirr)
-[X] 9d6 Attack (all tricks)
-[X] 1d6 Defense
-[X] 27d6 Intercept (all tricks)
-[X] Put 2 Orthstirr into 4 layers of Reinforce Shield before the combat begins (-2 Orthstirr)
-[X] As soon as the squire is in range, toss a 9d6 (10d6 w/Hugareida) Kindle Spinner attack (-5 Orthstirr) at his mount, hoping to force the horse to panic, or both of them to close.
-[X] Prepare three 9d6 (11d6 w/Hugareida) Inertia-Arresting-Throw Intercepts to use if people other than Halla are attacked at range (-6 Orthstirr each). If he charges while we still have one ready, use it on his horse's legs to stop the charge.
-[X] In response to any Trick Attack directly targeting us use Halting Vortex (-4 Orthstirr)...if an attack somehow gets through that attempt to Sidestep (-4 Orthstirr) if possible. If our fylgja is attacked use Halting Vortex no matter what (-4 Orthstirr). If we can also shield Abjorn on top of us and our Fylgja (or the Fylgja has fled) use Halting Vortex to defend him as well if it looks like his own defenses have failed (-4 Orthstirr).
-[X] Tactics – Bring up a shieldwall and advance as a unit, Abjorn taking point. Bring out Halla's Fylgja and keep it with her to play spotter, attempt to intercept incoming Javelin throws with Inertia Arresting Throw to support the defense. Stay together at all costs. Fylgja is to be veiled again when the range closes (using the mundane Defense die to leave if possible). If he charges, we use any remaining IAT to trip his horse, which should be nasty.
Basically, this is gambling a little on, if he makes 4 attacks, at least one will be against Halla. That seems like a reasonable gamble. It also encourages him to charge us since it proves we, too, have ranged attacks, and sets up a bit of a trap if he does so before exhausting his ranged options.
EDIT: Edited slightly to improve our IATs at the cost of relying entirely on HV to defend ourselves. That's worth it. Added emergency Sidestep use just in case...it seems unlikely that anything breaks Halting Vortex and even more unlikely that Sidestep could salvage things if it does...but it's still worth noting the contingency.