I think I can help with these two things,
on the first point he was very wrong. It is once per turn per crew, meaning each crew may cast it once per turn not once for each crew in the game.
on the second, I believe the bearskin cloak makes them immune to and . He would be immune to any blasts that come from the attacks but if the model was targetted by the attack it would still take the original damge from the weapon as it is not a blast. the bearskin armor makes the model immune to papa blowing up and take ya with me, but not the initial damge from the dynamite.
And of course, welcome to the forums