1. Don't know to be honest with you. Without having the rulebook to consult here at work, I would say your free to move, shoot, attack as normal. The unit is no longer locked in combat or pinned.
2. Once orbital strike starts, there is no stopping it. That's why it is important to keep your troops out the area, unless their sole purpose was to bait the enemy and die like true servants of the emperor
.
Glad to see someone using something besides the usual three exorcists in a list.