some newbie questions

[spacht]

1.: Which of these spells do fire damage and which don't? Astral fires, Hellfire, Bane fire, Magma eruption, Magma bolts

2.: How is fatigue calculated for multiple attacks and quickened attacks? ( I've run a test which seems to indicate that multiple attacks don't cause extra fatigue but quickened attacks do, is this correct? )

3.: I've read that communion slaves get a lot fatigue if their masters cast spells from paths the slaves don't know. Does anybody know the exact formula for this?

Thanks in advance