Questions that came up on a run, A few questions I was unable to answer Options

[Kurrel]

While running an adventure last night, a few queries came up that I was unsure of, hoping that I can get some clarification here.

If a mage has invisibility on himself and is standing in a room,
1.) What does another mage see when he assenses said room?
2.) What does a dematerialized spirit see?
3.) If the same spirit were materialized, would it see anything different?
4.) When the invisible mage casts a fireball, does that give a good indication of where the invisible mage is (This one caused the most argument of the night) ?

One character is shot for 7P and has 5 body, 2 willpower and 10 points of armour, downgrading the damage to stun. Is the roll body+armour (15) or willpower+armour (12)?

It's the second initiative pass of a combat round and a mage uses a simple action to summon a spirit and her next simple action to command it to attack a group of 5 gunmen taking cover on the opposite side of the street,
1) Does the spirit get to act in that initiative pass, or does it wait until the next combat round?
2) Is attacking group of X grunts a single service?
3) If a prime runner is taking cover with the 5 mooks, does 'attack everyone who was taking cover there' include this individual if he leaves the area?
4) Is the immunity power inherent to all spirits measured against the base damage of the weapon, or against the total damage from an individual attack? For example, a pistol does 5P but the shooter rolls 12 successes on the attack for an effective total of 17P damage. Against a force 3 water elemental with a hard armour of 6, is this attack kept or discarded?