1 After 40 anything will suit you, either Karmian, Plated or FP. After Lv 52 BW Light (OE for endgame).
Any melee weapon, most preferably a dagger or sword as they crit more.
2 wit for cast speed and heal crits and 2 str -dex.
3 Shadow
4 Make sure to have VR stew all times. Team up with a Warcryer preferably for VR Lv3.
Try to farm/buy Phantom Cubic as soon as you become a PS, you can leave Spark Cubic for later 70+.
Level up Servitor Heal only till you reach 56, personally I don't think it's worth to go further.