1. Sure thing, they cannot be affected by morale results, but indeed they can cause an enemy unit to retreat

By "cannot be effected", does that mean that Bone Horrors don't take damage by not retreating? So they ignore morale results rolled against them by not retreating and not taking damage through their not retreating?

By "cannot be effected", does that mean that Bone Horrors don't take damage by not retreating? So they ignore morale results rolled against them by not retreating and not taking damage through their not retreating?

Bone Horrors cannot resolve retreat effects, meaning that if they are ever forced to retreat (and are not supported) they take damage instead of retreating. They do not ignore morale results.