ex. Pyrotechnics increases all fire damage by 5%
a staff that does fire damage benefits from this in it's melee attack? yes/no
Yes, just tested this and verified it using a wand, staff and a piece of +2 Pyrokinetics gear.
ex. two handed skill increases damage with two handed weapons by 5% and crit modifier by 5%.
fireball spell does or does not benefit from the damage increase and or the crit modifier (assuming you have savage sortilege talent)?
Fireball would not benefit from the damage increase to 2H weapons. It would benefit from the Critical chance on the weapon with Savage Sortelige.